Search

Achnanthidium enigmaticum E.Morales & Manoylov sp. nov. Figs 43 –59 (LM), 60–65 (SEM) Description:— Frustules rectangular in girdle view (not shown here). Valves linear to elliptic with rostrate apices (Figs 43 –59). Length: 17.0–54.4 µm, width: 4.1–5.2 µm, stria density 23–26 (up to 29 toward apices) in 10 µm in RV, and 23–26 (up to 34 toward apices) in 10 µm in SV. Hymenes, girdle bands and plastids not determined. RV with lanceolate, raised axial area (more in internal Fig. 61 than in external view Fig. 62), broad at valve ends (Figs 60–63), becoming enlarged in the central area where it assumes a circular or rhomboid shape (Figs 43 –53). Central area with slightly raised central nodule in external view (Figs 60, 61), clearly raised in internal view (Figs 62 and 63), and with shortened striae on both sides (Figs 60–63). Virgae wider than striae becoming slender toward the valve apices, lower with respect to axial area and at same level as striae in external and internal views (Fig. 61). Raphe filiform and straight, externally with proximal ends expanded and opposite to each other (Fig. 60, white arrows), and distal fissures expanded, close-hooked in shape and strongly deflected toward same direction, surfacing gradually at valve face/mantle junction, within the striation region (Fig. 61, white arrows). Internally, proximal raphe ends curved and deflected in opposite directions (Fig. 63, white arrow), distal raphe ends terminate in low helictoglossae located at a distance from valve apices (Fig. 63, black arrow). Striae varying from parallel at valve central area, only sometimes becoming slightly convex toward the apices, short striae on both sides of central area present (Figs 60–63). Areolae visible under LM, round, elliptic or slit-like (Figs 43 –53). A single row of elliptic areolae present on valve mantle, more slit-like in shape and interrupted by clear area at valve apex (Figs 60, 63). A clear area runs around the edge of the face/mantle junction (Figs 60–61). SV with sunken lanceolate axial area (only observed in external view), broad at valve ends (seen as an expansion as the distal end of striation is reached) (Figs 64, 65). Virgae wider than striae, becoming slender toward valve apices, but in general wider than those in RV at the same region (compare Figs 63 and 65). Striae at same level as virgae. Central area with evenly spaced striae, rarely shortened (Figs 64, 65). Type locality:— U.S.A. Texas, Uvalde County, Sabinal River, 29.491 N, 99.493 W, NAWQA August 7 th, 1996 (holotype slide ANSP GC 102382 a = Fig. 48) Etymology:— The species epithet refers to the fact that this diatom has remained undiscovered despite the rather long history of studies of algae, particularly diatoms, in Texas. Ecology for both taxa:— While A. lucectorii sp. nov. was found in 3.1% relative abundance in a count of 600 valves, A. enigmaticum sp. nov. was only found in a relative abundance of Encyonema neogracile Krammer (1997a: 177, with a relative abundance of 26.8%), Delicata delicatula (Kützing) Krammer (2003: 113, 20.5%), Encyonopsis microcephala (Grunow) Krammer (1997b: 91, 11.8%), Ulnaria ulna (Nitzsch) Compère (2001: 100, 7.8%), Achnanthidium caledonicum (Lange-Bertalot) Lange-Bertalot (1999: 277, 5.3%), Navicula cryptotenella Lange-Bertalot (1985: 62, 3.0%) and other species in relative abundances A. caledonicum and N. cryptotenella, the type locality could have a calcareous, alkaline influence (Van Dam et al. 1994, Hofman et al. 2011). K. Manoylov recently found, in periphyton collections from May 2022, A. lucectorii sp. nov. in Roy Creek, Austin, TX (relative abundance A. enigmaticum sp. nov. in Hamilton Creek and Deadmans Creek, close to Austin, TX (relative abundance, Published as part of Morales, Eduardo A. & Manoylov, Kalina M., 2023, Achnanthidium lucectorii sp. nov. and A. enigmaticum sp. nov., novel diatoms (Bacillariophyta, Achnanthidiaceae) from Texas, U. S. A., pp. 1-20 in Phytotaxa 592 (1) on pages 6-8, DOI: 10.11646/phytotaxa.592.1.1, http://zenodo.org/record/7835613, {"references":["Krammer, K. (1997 a) Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 1. Allgemeines und Encyonema Part. Bibliotheca Diatomologica 36: 1 - 382.","Krammer, K. (2003) Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. Diatoms of Europe, Diatoms of the European Inland waters and comparable habitats 4: 1 - 529.","Krammer, K. (1997 b) Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 2. Encyonema Part., Encyonopsis und Cymbellopsis. Bibliotheca Diatomologica 37: 1 - 469.","Compere, P. (2001) Ulnaria (Kutzing) Compere, a new genus name for Fragilaria subgen. Alterasynedra Lange-Bertalot with comments on the typification of Synedra Ehrenberg. In: Jahn, R., Kociolek, J. P., Witkowski, A. & Compere, P. (Eds.) Lange-Bertalot Festschrift. Studies on diatoms dedicated to Prof. Dr. Dr. h. c. Horst Lange-Bertalot on the occasion of his 65 th birthday, A. R. G. Gantner Verlag K. G., Ruggell, pp. 97 - 101.","Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus Achnanthes Bory (sensu lato). Iconographia Diatomologica 6: 270 - 283.","Van Dam, H., Mertens, A. & Sinkeldam, J. (1994) A coded checklist and ecological indicator values of freshwater diatoms from the Netherlands. Netherlands Journal of Aquatic Ecology 28: 117 - 133. https: // doi. org / 10.1007 / BF 02334251"]}

Two new species, Achnanthidium lucectorii sp. nov., belonging to the A. minutissimum complex (species with straight terminal raphe ends), and A. enigmaticum sp. nov., within the A. pyrenaicum complex (species with hooked terminal raphe fissures), are described from Texas, U.S.A. utilizing light and scanning electron microscopy. Achnanthidium lucectorii sp. nov. has a raphe valve with striae located toward the apices composed of polygonal areolae, a marked stauros, a non-expanded raphe fissure, with straight (non-dilated) proximal ends, and distal ends extending onto the valve mantle. Internally, its raphe valve is flat, the proximal ends of the raphe end in small capitate expansions, and the distal ends terminate in low helictoglossae that fuse with the apices by a low apical siliceous thickening. In turn, its sternum valve is unique in that it is mostly flat in inner view, except at the central nodule, which is slightly raised. In turn, A. enigmaticum sp. nov. externally has a raphe valve with raphe distal ends shaped like a closed hook, at these ends the raphe slit surfaces at the valve face/mantle junction; its axial area is raised in external and internal views, with the virgae and striae in a lower position. These and other traditionally considered features are compared in detail with taxa morphologically similar to each of the new species. The significance of these features is discussed based on a literature survey, and the implications of considering the valve surface topography and the external and internal details of the raphe and central area are assessed. The latter, in favor of a continued morphological exploration of Achnanthidium until molecular studies are appropriately integrated into current morphological approaches used in the taxonomy of the genus.

Achnanthidium lucectorii E.Morales & Manoylov sp. nov. Figs 1–36 (LM), 37–42 (SEM) Description:— Frustules apically sigmoidally arched (in an open V-shaped girdle view), producing a raphe valve with a concave valve center (Figs 22, 23). Valves elliptic with swollen central area and subcapitate apices (Figs 1–21, 24–36), less noticeable in smaller valves. Length: 10.2–35.7 µm, width: 3.1–4.3 µm, stria density 26–28 (up to 30 toward apices) in 10 µm in RV, and 26–27 (up to 32 toward apices) in 10 µm in SV, 1–4 areolae per stria on both valves. Hymenes, girdle bands and plastids not determined. RV with narrow, lanceolate, raised axial area (externally [Figs 37–39] and internally [Fig. 40]), tapering into a pointy end at valve apex, becoming enlarged in central area where it connects with the central stauros (Figs 37–40). Central stauros with bow-tie shaped fascia (rarely apically rhomboid in some larger valves) (Figs 1–21), with raised central nodule in external view (Figs 37–39, 41), flat in internal view (Fig. 40). Virgae wider than striae except at valve ends where they become slender and rod-shaped, straight or zig-zagged due to polygonal shape of areolae (Figs 38, 39). Virgae lower with respect to axial area and at same level as striae in internal and external views (Figs 37–40). Raphe uniformly filiform and straight, with proximal ends opposite to each other (Figs 37–39). Distal fissures straight and extending over striation regions at both poles (Fig. 39, white arrows). Internally, proximal raphe ends with a small capitate terminus (Fig. 40, white arrows) and distal ends terminating in low helictoglossae fused with a low thickening of valve apex (Fig. 40, black arrow). Striae varying from convex toward valve central area (striae frequently lacking or being shorter on central stauros) becoming extremely convex and noticeably denser toward apices (Figs 37–39, 41). Areolae round or elliptic toward the central sternum, becoming transapically elongated toward valve face/mantle transition, and densely packed and polygonal at valve extremes (Fig. 38, open arrows), usually with two large areolae on both sides of distal raphe end (Figs 37, 39). A single row of slit-like areolae present on valve mantle, stopping short of the very apex (unclearly seen in Fig. 40). A clear area runs around edge of the face/mantle junction (Figs 37–39). SV (Figs 41, 42) with wider, flat (only observed in internal view) lanceolate axial area, more or less broad at valve ends. Central nodule is only slightly raised internally. Virgae of same characteristics as in RV, but at same level as striae and axial area (only internal views available). Striae of same general characteristics as those of RV, except they are evenly spaced (some are short) at valve central area, they become less convex toward the valve apices, and single row of elongated striae on the valve mantle are continuous around valve apex. The clear area around edge of the face/mantle junction is less noticeable. Type:— U.S.A. Texas, Uvalde County, Sabinal River, 29.491 N, 99.493 W, NAWQA, August 7 th, 1996 (holotype slide ANSP GC 102382 a = Fig. 10) Etymology:— The species epithet honors our late colleague Luc Ector. Luc promoted a major advancement in the taxonomy of the genus Achnanthidium through a series of courses and workshops that were the foundation of the taxonomy used in the European Water Framework Directive. The special issue in Algological Studies (2011: 136/137), edited by Luc and the result of one of those workshops, presented critical analyses of type material and new species in Achnanthidium from around the world, a foundation for current studies in this genus.

During an evaluation of the diatom diversity and water quality of a small brook near Morogoro (Tanzania), an unknown Planothidium species was observed that could not be identified using the currently available literature. The past 10 years, a large number of Planothidium species has been revised resulting in a better characterisation of some well-known taxa such as P. lanceolatum (Brébisson ex Kützing 1846: 247) Lange-Bertalot (1999: 287), P. frequentissimum (Lange-Bertalot 1993: 4) Lange-Bertalot (1999: 282) and P. delicatulum (Kützing 1844: 75) Round & Bukhtiyarova (1996: 353), but also in the description of a lot of new species (Compère & Van de Vijver 2009, Jahn et al. 2017, Kulaš et al. (2020), N’Guessan et al. 2014, Stancheva 2019, Stancheva et al. 2020, Van de Vijver et al. 2013, 2018, Wetzel et al. 2013, 2014, 2019). Several of these studies dealt with Planothidium species from the African Continent. Compère & Van de Vijver (2009) analysed and illustrated the type material of P. engelbrechtii (Cholnoky 1955: 16) Round & Bukhtiyarova (1996: 353), whereas N’Guessan et al. (2014) discussed the morphology and taxonomic history of two species formerly described by Carter & Denny in 1982: P. miotum (J.R.Carter & Denny 1982: 286) Lange-Bertalot (1999: 278) & P. piaficum (J.R.Carter & Denny 1982: 286) C.E.Wetzel & Ector (in N’Guessan et al. 2014: 460), completed with the description of P. comperei C.E.Wetzel et al. (in N’Guessan et al. 2014: 456), a new Planothidium species from Ivory Coast.

Planothidium africanum Van de Vijver, Gogne, Hoogsteyns, Van de Velde, Vlaminck, Kabota, Teunen & C.E.Wetzel sp. nov. (Figs 1–28 LM, 29–35 SEM) Valves lanceolate (in the largest specimens) to elliptic-lanceolate with distinctly convex margins and protracted, rostrate but truncated apices. Valve dimensions (n=40): length 11–25 μm, width 5.5–6.5 μm. Rapheless valve (Figs 1–14, 29, 30, 33 & 35): Axial area usually narrow, straight, linear, occasionally weakly lanceolate and broadening near the central area. Irregularly shaped, shallow depressions present in both central and axial area (Figs 29, 33). Central area with a unilateral large horseshoe-shaped hyaline area. Cavum distinctly visible, internally passing over the neighboring striae (Figs 30, 35). Striae on the opposite site only weakly to almost shortened. Striae parallel to weakly radiate near the central area, becoming more radiate near the apices, 15–16 in 10 µm. Striae multiseriate, composed of three rows of small, rounded areolae at the valve margins, becoming biseriate towards the axial area (Fig. 29, 33). On the mantle, irregular groupings of small, rounded areolae present, continuing the valve face striae on the mantle (Fig. 33). Internally, striae located in deep grooves (Fig. 30). Raphe valve (Figs 15–28, 31, 32 & 34): Axial area very narrow, linear, not widening towards the central area. Central area asymmetrical, rectangular to slightly wedgeshaped, bordered on each side by 2–3 shortened striae, whereas on the opposite side, striae either lacking or extremely shortened. Raphe branches straight with expanded, drop-like central raphe pores (Fig. 31). Terminal raphe fissures unilaterally deflected (Fig. 31). Striae weakly radiate throughout the entire valve, 14–16 in 10 μm. Internally, central nodule clearly raised (Fig. 32). Internal central raphe endings weakly deflected into opposite directions, terminating onto the central nodule (Fig. 32). Internally, striae located in broad, deep grooves (Fig. 32). Cingulum composed of multiple open girdle bands (Fig. 34). Type:— TANZANIA. Morogoro, sample L10 stone, coll. date VII.2022, leg. Van de Velde (holotype slide BR-4778= Fig. 6, isotype slide 422, University of Antwerp, Belgium). PhycoBank registration: — www.PhycoBank.org/103609 Ecology & associated diatom flora:— Sample L10 Stone (S 06° 49’ 00.1” / E 037° 42’ 56.8”) was collected from some submerged stones in a small, shallow (Navicula species [N. rostellata Kützing (1844: 95), N. schroeteri Meister (1932: 38), N. symmetrica R.M. Patrick (1944: 5)], Achnanthidium exiguum (Grunow in Cleve & Grunow 1880: 21) Czarnecki (1994: 157), Cocconeis cf. euglypta, Planothidium africanum, P. rostratum (Østrup 1903: 35) Lange-Bertalot (1999: 279), several (non-identified) Gomphonema species, and Geissleria cf. decussis with lower numbers of Seminavis strigosa (Hustedt 1949: 44) Danielidis & Economou-Amilli (in Danieldis & Mann 2003: 30), Halamphora sp. and Pleurosigma salinarum (Grunow 1878: 116) Grunow (in Cleve & Grunow 1880: 54). Based on Lange-Bertalot et al. (2017) and Taylor et al. (2007), this diatom flora is typical for eutrophic, freshwater with higher electrolyte content to even brackish, and β- to α-mesosaprobic conditions, pointing to a high degree of pollution. Taxonomic comments:— Table 1 lists the morphometric features of several similar Planothidium species. Planothidium africanum has a distinct cavum, excluding several species bearing a comparable valve outline but with a sinus from being conspecific. Planothidium californicum Stancheva & N.Kristan (in Stancheva et al. 2020: 8) has a similar valve outline and similar valve dimensions, but lacks the typical cavum and hence can be relatively easily separated from the new species. Planothidium dubium (Grunow in Cleve & Grunow 1880: 23) Round & Bukhtiyarova (1996: 352) and P. reichardtii Lange-Bertalot & Werum (in Werum & Lange-Bertalot 2004: 172) have a similar elliptic-lanceolate valve outline with truncated, rostrate apices and an asymmetrical central area in the raphe-bearing valve. But both taxa also lack the distinct cavum structure excluding hence all conspecificity. The African species discussed in N’Guessan et al. (2014) sufficiently differ not to be confused with P. africanum. Planothidium comperei shows the highest resemblance based on its valve outline, although most valves have more convex valve margins. The stria structure of the rapheless valve also shows some similarity with the multiseriate nature of the striae at the valve margins becoming biseriate near the axial area. But the species can be separated from P. africanum in having an almost symmetrical central area in the raphe-bearing valve with a more radiate striation pattern, contrary to P. africanum having more parallel striae and a distinctly asymmetrical central area with on one side an almost complete lack of (or very shortened) striae. The most similar species is P. incuriatum C.E.Wetzel, Van de Vijver & Ector, split off from P. biporomum (M.H. Hohn & Hellerman 1963: 273) Lange-Bertalot (1999: 275) in 2013. Most likely, P. africanum, P. incuriatum and P. biporomum are close to each other, given a similar shape in cavum structure, a similar stria structure with a multiseriate base at the valve margin and a biseriate part at the axial area, and similar shallow markings in the axial and central area. However, Planothidium incuriatum has a more elongated, slender valve outline with more protracted apices, a symmetrical central area in the raphe-bearing valves (contrary to the distinctly asymmetrical central area in P. africanum) and slightly wider valves (6.5–7.0 µm versus 5.5–6.5 µm in P. africanum). The striae in the rapheless valve of P. africanum have a distinct grouping of 3 series of areolae at the valve margin, a feature not observed in P. incuriatum that have a very faint third series of areolae at the margin (see for instance Wetzel et al. 2003, fig. 51). This grouping is also visible in the mantle areolae (Fig. 33). Finally, other rostrate, cavum-bearing taxa such as P. rostratum (present in the same sample as P. africanum) and P. rostratoholarcticum Lange-Bertalot & Bąk (in Bąk & LangeBertalot 2014: 354) differ in having multiple slit-like grooves in their axial and central area, so far not observed in P. africanum. Contrary, P. africanum possesses an irregular pattern of small, shallow depressions in the axial area, not seen in P. rostratum and P. rostratoholarcticum. Wetzel et al. (2019) discuss several small-celled cavum-bearing Planothidium species such as P. frequentissimum but they can all be separated based on their valve dimensions (usually shorter and/or narrower), shape of the apices (typically broadly rounded, hardly protracted in P. frequentissimum) and valve outline, most of them being more strictly lanceolate instead of the elliptic-lanceolate valves observed in P. africanum., Published as part of Vijver, Bart Van De, Gogne, Britt, Hoogsteyns, Gabrielle, Velde, Levente Van De, Vlaminck, Luna, Kabota, Sija A., Teunen, Lies & Wetzel, Carlos E., 2023, Planothidium africanum sp. nov., a new freshwater diatom (Bacillariophyta) species from Tanzania, pp. 281-286 in Phytotaxa 585 (4) on pages 282-284, DOI: 10.11646/phytotaxa.585.4.4, http://zenodo.org/record/7703860, {"references":["Kutzing, F. T. (1844) Die Kieselschaligen Bacillarien oder Diatomeen. Nordhausen, pp. [i-vii], [1] - 152.","Meister, F. (1932) Kieselalgen aus Asien. Gebruder Borntraeger, Berlin, pp. [1] - 56.","Patrick, R. M. (1944) Estudo Limnologico e Biologico das Lagoas da regiao Litoranea Sul-Riograndense II. Some New Diatoms from the Lagoa dos Quadros. Boletim do Museu Naciona, nova serie, botanica 2: 1 - 6.","Cleve, P. T. & Grunow, A. (1880) Beitrage zur Kenntniss der arctischen Diatomeen. Kongliga Svenska Vetenskaps-Akademiens Handlingar 17 (2): 1 - 121.","Czarnecki, D. B. (1994) The freshwater diatoms culture collection at Loras College, Dubuque, Iowa. In: Proceedings of the 11 th International Diatom Symposium. Memoirs of the California Academy of Sciences 17: 155 - 174.","Ostrup, E. (1903) Freshwater diatoms. In Flora of Koh Chang. Part VII. Contributions to the knowledge of the Gulf of Siam. Preliminary Report on Botany. Results Danish Expedition to Siam (1899 - 1900). Botanisk Tidsskrift 25 (1): 28 - 41.","Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus Achnanthes Bory (sensu lato). Iconographia Diatomologica 6: 270 - 283.","Hustedt, F. (1949) Diatomeen von Sinai-Halbinsel und aus dem Libanon-Gebiet. Hydrobiologia 2: 24 - 55.","Grunow, A. (1878) Algen und Diatomaceen aus dem Kaspischen Meere. In: Schneider, O. (Ed.) Naturwissenschaftliche Beitrage zur Kenntnis der Kaukasuslander, auf Grund seiner Sammelbeute. Dresden Burdach, Dresden, pp. 98 - 132.","Lange-Bertalot, H., Hofmann, G., Werum, M. & Cantonati, M. (2017) Freshwater benthic diatoms of Central Europe: over 800 common species used in ecological assessment. English edition with updated taxonomy and added species. Koeltz Botanical Books, Schmitten- Oberreifenberg, 942 pp.","Taylor, J. C., Harding, W. R. & Archibald, C. G. M. (2007) An Illustrated Guide to Some Common Diatom Species from South Africa An Illustrated Guide to Some Common Diatom Species from South Africa. WRC Report No TT 282 / 07. Water Research Commission, Pretoria, pp. 1 - 178 pls.","Stancheva, R., Kristan, N. V., Kristan, W. B, III & Sheath, R. G. (2020) Diatom genus Planothidium (Bacillariophyta) from streams and rivers in California, USA: diversity, distribution and autecology. Phytotaxa 470 (1): 1 - 30. https: // doi. org / 10.11646 / phytotaxa. 470.1.1","Round, F. E. & Bukhtiyarova, L. (1996) Four new genera based on Achnanthes (Achnanthidium) together with a re-definition of Achnanthidium. Diatom Research 11 (2): 345 - 361. https: // doi. org / 10.1080 / 0269249 X. 1996.9705389","Werum, M. & Lange-Bertalot, H. (2004) Diatoms in springs from Central Europe and elsewhere under the influence of hydrologeology and anthropogenic impacts. Iconographia Diatomologica 13: 3 - 417.","N'Guessan, K. R., Wetzel, C. E. Ector, L., Coste, M., C. Cocquyt, C., Van de Vijver, B., Yao, S. S., Ouattara, A., Kouamelan, E. P. & Tison- Rosebery, J. (2014) Planothidium comperei sp. nov. (Bacillariophyta), a new diatom species from Ivory Coast. Plant Ecology and Evolution 147 (3): 455 - 462. https: // doi. org / 10.5091 / plecevo. 2014.981","Hohn, M. H. & Hellerman, J. (1963) The taxonomy and structure of diatom populations from three eastern North American rivers using three sampling methods. Transactions of the American Microscopical Society 82 (3): 250 - 329.","Wetzel, C. E., Van de Vijver, B., Hoffmann, L. & Ector, L. (2013) Planothidium incuriatum sp. nov. a widely distributed diatom species (Bacillariophyta) and type analysis of Planothidium biporomum. Phytotaxa 138 (1): 43 - 57. https: // dx. doi. org / 10.11646 / phytotaxa. 138.1.6","Wetzel, C. E., Van de Vijver, B., Blanco, S. & Ector, L. (2019) On some common and new cavum-bearing Planothidium (Bacillariophyta) species from freshwater. Fottea 19 (1): 50 - 89. https: // doi. org / 10.5507 / fot. 2018.016","Bak, M. & Lange-Bertalot, H. (2014) Four small-celled Planothidium species from Central Europe proposed as new to science. Oceanological and Hydrobiological Studies 43 (4): 346 - 359. https: // doi. org / 10.2478 / s 13545 - 014 - 0152 - 9"]}

Cocconeis Ehrenberg species (Bacillariophyceae) are documented from benthic samples collected along the Seogwipo coast of Jeju Island, the southernmost region of Korea. The 25 taxa were identified from seaweeds, sand, and sediments, their morphological features are described, and the distributions of the taxa are summarized. Three groups of Cocconeis e.g., Cocconeis dirupta var. flexella, C. pseudomarginata var. intermedia, Cocconeis scutellum, and their similar taxa were dominant in this area. Many other Cocconeis that grows mainly along the coasts of warmer oceans were also identified. The floristic study reveals the existence of rare or retrieved species that were not well known until recently, and expands some of their geographical distributions; Cocconeis cf. callosa, C. conspicua, C. cyclophora var. decora, C. cyclophora var. meisteri, C. delicata, C. schmidtii, C. shikinensis, C. suzukii, C. voigtii. In this floristic study, 14 Cocconeis taxa are new records in South Korea.

Achnanthidium peruvianum E.Morales & Ector in Morales et al. (2011: 121) (Figs 166–193) Synonym: Achnanthes kryophiloides M.H.Hohn in Patrick et al. (1966), p. 468, pl. 1, Figs 5, 6 Morphometric features:— 8.0–20.2 µm long; 2.3–4.3 µm wide; 28–34 striae in 10 µm; striae mainly composed of 4–5 areolae. Taxonomical remarks:— The species presents similar morphological features to another South American species called Achnanthidium sehuencoensis, which has almost the same valve outline. However, SEM analysis separated the two due to the deflected terminal raphe fissures, the non-expanded central raphe fissures, and lower stria density (20–24/10 µm, Morales et al. 2009) compared to A. peruvianum. Achnanthidium petersenii (Hustedt) C.E.Wetzel, Ector & Jüttner (in Jüttner et al. 2019: 66) has wider fascia on the raphe valve. However, on the rapheless valves, the axial area is moderately broad, and the central area broadly rhombic-lanceolate (Jüttner et al. 2019). In A. peruvianum, the axial area is narrow and linear, while the central area is undifferentiated with short striae (Morales et al. 2011). Distribution and ecological information:— Achnanthidium peruvianum was described from the Rondos River in Peru, South America (Hohn in Patrick et al. 1966). In our samples, the species was rare (abundance, Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on page 207, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Morales, E. A., Ector, L., Fernandez, E., Novais, M. H., Hlubikova, D., Hamilton, P. B., Blanco, S., Vis, M. L. & Kociolek, J. P. (2011) The genus Achnanthidium Kutz. (Achnanthales, Bacillariophyceae) in Bolivian streams: a report of taxa found in recent investigations. Algological Studies 136 - 137: 89 - 130. https: // doi. org / 10.1127 / 1864 - 1318 / 2011 / 0136 - 0089","Morales, E. A., Fernandez, E. & Kociolek, J. P. (2009) Epilithic diatoms (Bacillariophyta) from cloud forest and alpine streams in Bolivia, South America 3: diatoms from Sehuencas, Carrasco National Park, Department of Cochabamba. Acta Botanica Croatica 68 (2): 263 - 283.","Juttner, I., Wetzel, C. E., Williams, D. M. & Ector, L. (2019) Investigations of the type materials of Achnanthes parallela J. R. Carter and Achnanthes petersenii Hustedt (Bacillariophyceae) with comments on the genus Rossithidium Round & Bukhtiyarova. Botany Letters 167 (1): 57 - 69. https: // doi. org / 10.1080 / 23818107.2019.1668297"]}

Achnanthidium peetersianum C.E.Wetzel, Jüttner & Ector in Wetzel et al. (2019: 345) (Figs 144–165) Morphometric features:— 7.6–12.3 µm long; 2.0–2.7 µm wide; 29–34 striae in 10 µm; striae mainly composed of 3–5 areolae. Taxonomical remarks:— Our population is in agreement with the type species, besides it has slightly narrower valves when compared to the French population (2.8–3.3 μm, Wetzel et al. 2019). This species has narrow valves with subcapitate to small capitate apices, similar to A. macrocephalum (Hustedt) Round & Bukhtiyarova (1996: 349), although the latter taxon presents broadly capitate apices. Despite being difficult to separate, a reevaluation of A. macrocephalum type material was recently published in the same study as A. peetersianum (Wetzel et al. 2019). Using SEM micrographs, the authors showed that A. peetersianum presented predominantly rounded areolae and had a higher density per stria, while A. macrocephalum striae are composed of 1–2 elongated areolae of different lengths. Moreover, the axial area of the rapheless valve of the latter taxon is expanded, widening towards the central area. Recently, Yu et al. (2019) described two small species that resemble ours: A. subtilissimum P.Yu, Q. -M.You & Q.-X.Wang (in Yu et al. 2019: 161) and A. limosua P.Yu, Q. -M.You & Q.-X.Wang (in Yu et al. 2019: 158). The first species is likely a synonym of A. macrocephalum, and the second presents visibly larger valves (3.2–4.0 µm) than A. peetersianum. Achnanthidium indistinctum also bears several similarities with A. peetersianum. They can be distinguished in girdle view by the apparently thickened striae in the first taxon, which is not visible in our specimens (see Figs 158, 159). Concerning the valve view, A. indistinctum presents rostrate apices and an almost nonexistent central area that never forms a fascia. On the other hand, A. peetersianum exhibits subcapitate to capitate apices and a small rounded central area that rarely forms a fascia. Notably, SEM analysis can also help separate both taxa due to the distal raphe ends straight in A. indistinctum and bent in our specimens. Despite the slightly narrower valves in the latter taxon (1.8–2.2 µm, Van de Vijver & Kopalová 2014), the metric features of these two species overlap. Achnanthidium reimeri (Camburn) Ponader & Potapova (2007: 235) has a similar valve outline with our population, however, it presents longer and wider valves and a rhomboid central area on the rapheless valve (Ponader & Potapova 2007). Distribution and ecological information:— Recently described from Le Sauvigny River in France, it was one of the most well-distributed species found in this study (40 % of occurrence). It is plausible that this taxon was previously identified in Brazilian publications as A. macrocephalum. In this study, A. peetersianum occurred in all of the sampled habitats. Its ecological preference was for slightly acidic (pH optimum of 6.6–6.7), electrolytic-poor (optimum of 28.2–49 μS∙ cm-1) and oligo- to mesotrophic waters (TP optimum of 14.9–27.1 μg∙L- 1, TN optimum of 374.4–519.4 μg∙L- 1). We also observed this species in enriched waters (TP> 50 μg∙L- 1)., Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on pages 204-205, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Wetzel, C. E., Juttner, I., Gurung, S. & Ector, L. (2019) Analysis of the type material of Achnanthes minutissima var. macrocephala (Bacillariophyta) and description of two new small capitate Achnanthidium species from Europe and the Himalaya. Plant Ecology and Evolution 152 (2): 340 - 350. https: // doi. org / 10.5091 / plecevo. 2019.1628","Bukhtiyarova, L. & Round, F. E. (1996) Revision of the genus Achnanthes sensu lato. Psammothidium, a new genus based on A. marginulatum. Diatom Research 11: 1 - 30. https: // doi. org / 10.1080 / 0269249 X. 1996.9705361","Yu, P., You, Q. - M., Pang, W. - T., Cao, Y. & Wang, Q. - X. (2019) Five new Achnanthidiaceae species (Bacillariophyta) from Jiuzhai Valley, Sichuan Province, Southwestern China. Phytotaxa 405 (3): 147 - 170. https: // doi. org / 10.11646 / phytotaxa. 405.3.5","Van de Vijver, B. & Kopalova, K. (2014) Four Achnanthidium species (Bacillariophyta) formerly identified as Achnanthidium minutissimum from the Antarctic Region. European Journal of Taxonomy 79: 1 - 19. https: // doi. org / 10.5852 / ejt. 2014.79","Ponader, K. C. & Potapova, M. G. (2007) Diatoms from the genus Achnanthidium in flowing waters of the Appalachian Mountains (North America): Ecology, distribution and taxonomic notes. Limnologica 37 (3): 227 - 241. https: // doi. org / 10.1016 / j. limno. 2007.01.004"]}

Achnanthidium lusitanicum Novais & M.Morais in Novais et al. (2015: 129) (Figs 45–99) Morphometric features:— 6.5–16.5 µm long; 2.6–3.4 µm wide; 30–34 striae in 10 µm; striae mainly composed of 4–6 areolae. Taxonomical remarks:— Achnanthidium lusitanicum shares morphological similarities with A. eutrophilum (Lange-Bertalot) Lange-Bertalot (1999: 271) but our species has slender valves narrower than the latter taxon, which has rhombic-lanceolate to rhombic-elliptical frustules in small specimens and valve apices bluntly rounded to cuneate. Also, A. lusitanicum have a higher stria density (A. eutrophilum: 3.2–5.8 µm wide, striae 25–30/10 µm, Hlúbiková et al. 2011). Achnanthidium caravelense Novais & Ector (in Novais et al. 2011: 142) is similar to A. lusitanicum when analyzed by LM and SEM. However, it differs from A. lusitanicum mainly by the elliptic raphe valve with almost linear margins. The SEM images show that A. caravelense presents a lower number of areolae per striae (3–4, Novais et al. 2011). The valve outline of Achnanthidium palmeti Gassiole, Le Cohu & M.Coste (2013: 22) is very similar to A. lusitanicum, and the cell metrics overlap. However, some A. palmeti specimens have slightly wider valves (2.7–4.6 μm, Gassiole et al. 2013). The main character differing both species is the frustules that are arched with slightly recurved apices in A. palmeti and its terminal raphe fissures of the raphid valve are deflected towards the same side. Indeed, our species has straight raphe fissures and an almost flat valve face. In São Paulo state, Achnanthidium saprophilum (H.Kobayasi & Mayama) Round & Bukhtiyarova (1996: 349) shows valves with no inflation in the central portion as A. lusitanicum, and it also presents lower stria density (26–30 in 10 μm). Besides that, A. saprophilum showed presence of areolae with different shapes, a feature not observed in A. lusitanicum. In addition, a similar Brazilian population was cited as A. jackii by Bartozek et al. (2018). However, the cited species had linear-lanceolate valves with broadly rounded and rostrate apices, a central area always forming a fascia and lower stria density (28–30/10 µm, Van de Vijver et al. 2018). Notably, the central area of A. lusitanicum rarely produces a unilateral fascia, being often absent or small rounded with some shortened striae. Distribution and ecological information:— The taxon was found in all three habitats (occurrence of 10 %), but it was more often found in surface sediments from reservoirs. In the sediment assemblages, the ecological preferences of the taxa were for slightly alkaline (pH optimum of 7.3), medium cond. (optimum of 100.3 μS∙ cm-1) and eutrophic waters (TP optimum of 56.7 μg∙L- 1 and TN optimum of 1016.5 μg∙L- 1). It is worth mentioning that it also occurred in oligo- and mesotrophic waters.

The present study aims to expand the knowledge on Achnanthidium species occurring in tropical areas of southern Brazil. For this purpose, 345 samples from 179 sampling sites distributed throughout the state of São Paulo were analyzed for ‘monoraphid’ diatom diversity. This paper focuses on samples with a high abundance of Achnanthidium species. The permanent slides and stubs were observed using light and scanning electron microscopy. Morphometric analysis was performed to discriminate between similar species through the Elliptical Fourier Descriptors analysis. For this, valve outlines from Brazilian species were compared to those from type material available from the literature. The ecological optimum and tolerance was calculated for taxa that presented more than 10 % of occurrence per habitat. In total, 12 Achnanthidium species were observed. Six are described as new: Achnanthidium acutum sp. nov., A. brasiliense sp. nov., A. parvicapitatum sp. nov., A. paulistanum sp. nov., A. ritae sp. nov. and A. vandevijveri sp. nov. The morphometric analysis supported the differentiation between some taxa. Nine species, with occurrences of at least 10 % per habitat, had their ecological optimum and tolerance calculated. In general, these species prefer slightly acidic to neutral pH, medium electrolyte cond. and mesotrophic water conditions.

Achnanthidium brasiliense L.F.Costa & G.C.Marquardt sp. nov. (Figs 26–44) Description:— LM: Valves linear-lanceolate, with rostrate to subcapitate apices (Figs 26–38); 12.3–17.7 µm long, 2.5–2.9 µm wide. Raphe valve: axial area linear to linear-lanceolate, very narrow; central area small, rounded, almost absent, sometimes forming a rectangular fascia reaching one or both sides (Figs 26–33). Raphe filiform, straight. Transapical striae slightly radiate throughout the entire valve, becoming denser and more strongly radiate towards the apices (Figs 26–33); 26–30 in 10 µm. Rapheless valve: axial area narrow and linear, slightly widening towards the central area; central area absent or narrow lanceolate (Figs 34–38). Transapical striae slightly radiate throughout the entire valve, more spaced in the central area and sometimes lacking one stria unilaterally (Figs 34–38). Striae become denser towards the apices: 26–28 in 10 µm. SEM: Raphe terminating after the last stria in the border between the valve face and mantle (Figs 39, 40). Central and terminal raphe fissures straight and slightly expanded (Figs 39, 40). Striae mainly composed of 2–4 rounded to elongated areolae, sometimes slit-like shaped near the valve margin and becoming denser and wider near the distal ends (Figs 39–44). Mantle with one row of slit-like areolae (Figs 39, 44). Type:— BRAZIL. São Paulo state: São Paulo, Guarulhos, Tanque Grande reservoir, epiphython, 23° 22’ 29” S, 46° 27’ 31” W, S.A.Oliveira & D.C.Bicudo, 9th January 2014 (holotype SP-428935! = Fig. 34, isotype: BR-4615). Etymology:— The specific epithet brasiliense sp. nov. refers to the country of the type locality. Taxonomical remarks:— Achnanthidium brasiliense sp. nov. resembles A. minutissimum, however, an important feature in the separation of both taxa are the apices, which are always protracted in A. minutissimum. Observing the illustrations provided by studies of the type material (Novais et al. 2015, Marquardt et al. 2017) it is possible to notice the stronger curved valves in apices of A. minutissimum, showed by the difficulty in focusing on the apices under LM. Also, in SEM micrographs of A. minutissimum (Fig. 7B, C, E in Marquardt et al. 2017), the araphid valves present a strong curvature following the axial area, a feature not observed in our specimens. Regarding the morphometric features, A. brasiliense sp. nov. presents a lower stria density than the German A. minutissimum type material (30– 35/10 µm, Novais et al. 2015) and the type material population presented in Marquardt et al. (2017), which includes rapheless valves ranging from 30–34 striae in 10 µm in the middle. Although the number of striae in A. minutissimum is also denser near the distal ends, the appearance of areolae near the apices in the raphe valves of A. brasiliense sp. nov. change in size and shape, becoming larger. Achnanthidium minutissimum is a widely used name for a complex of morphologically similar species worldwide. The morphometric characteristics of all the species that belong to this complex and were observed in this study are summarized in Table 4. In addition, a quantitative shape analysis was carried out to separate A. brasiliense sp. nov. from A. minutisimum and its results are discussed below. Still concerning the similarities among A. brasiliense sp. nov. and other species, Novais et al. (2015) reanalyzed the type materials of two species resembling ours: A. microcephalum Kützing (1844: 75) and A. neocryptocephalum (Grunow in Van Heurck) Novais & Van de Vijver (in Novais et al. 2015: 116) ≡ A. minutissima var. cryptocephala Grunow (in Van Heurck 1880: 27). Achnanthidium brasiliense sp. nov. presents slender valves than A. microcephalum and the stria density is also a distinguishing feature (30–32 in 10 µm, Novais et al. 2015). Moreover, external terminal raphe fissures in A. microcephalum are slightly deflected in the same direction but straight in A. brasiliense sp. nov. Although the striae are also denser near the apices in both taxa, areolae become wider in A. brasiliense sp. nov. Regarding A. neocryptocephalum, their representatives always present a rectangular fascia in the raphe valve, a rare feature in A. brasiliense sp. nov. Achnanthidium jackii Rabenhorst (1861: 1003) (Rabenhorst 1861 –1862) described from “Quellwasser bei Salem” (Municipality of Baden-Württemberg state, southern Germany) was studied in full detail by Van de Vijver et al. (2018), has priority over A. neocryptocephalum, a new name for Achnanthes minutissima var. cryptocephala, thus is also a taxonomic synonym of A. jackii. Achnanthidium barbei Le Cohu & Pérès (in Pérès et al. 2014: 388) also belongs to the A. minutissimum -complex and presents a similar morphology. It never forms a fascia in the central area of the raphe valve and has protracted apices (Pérès et al. 2014). Distribution and ecological information:— In our dataset, A. brasiliense sp. nov. was the most frequent species (63 % of occurrence) observed in periphytic, planktonic and surface sediment assemblages (highest abundance: 72 % in SP469485). In all these habitats, the ecological preference of the species was for neutral waters (pH optimum of 6.8– 7.2), medium to high cond. (optimum of 64.3–148.7 μS∙ cm-1) and mesotrophic conditions (TP optimum of 25.5–46.4 μg∙L- 1 and TN optimum of 596–1303.8 μg∙L- 1). However, it also occurred in enriched waters (TP> 50 μg∙L- 1)., Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on page 196, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Novais, M. H., Juttner, I., Van de Vijver, B., Morais, M. M., Hoffmann, L. & Ector, L. (2015) Morphological variability within the Achnanthidium minutissimum species complex (Bacillariophyta): comparison between the type material of Achnanthes minutissima and related taxa, and new freshwater Achnanthidium species from Portugal. Phytotaxa 224 (2): 101 - 139. https: // doi. org / 10.11646 / phytotaxa. 224.2.1","Marquardt, G. C., Costa, L. F., Bicudo, D. C., Bicudo, C. E. M., Blanco, S., Wetzel, C. E. & Ector, L. (2017) Type analysis of Achnanthidium minutissimum and A. catenatum and description of A. tropicocatenatum sp. nov. (Bacillariophyta), a common species in Brazilian reservoirs. Plant Ecology and Evolution 150 (3): 313 - 330. https: // doi. org / 10.5091 / plecevo. 2017.1325","Kutzing, F. T. (1844). Die kieselschaligen Bacillarien oder Diatomeen. W. Kohne, Nordhausen. https: // doi. org / 10.5962 / bhl. title. 64360","Van Heurck, H. (1880) Synopsis des Diatomees de Belgique. Atlas. Anvers, Ducaju et Cie, pls 1 - 30.","Rabenhorst, L. (1861 - 1862) Die Algen Europa's, Fortsetzung der Algen Sachsens, resp. Mittel-Europas. Decades I-CIX, numbers 1 - 1600 (or 1001 - 2600). Dresden.","Van de Vijver, B., Wetzel, C. E. & Ector, L. (2018) Analysis of the type material of Achnanthidium jackii Rabenhorst (Bacillariophyta, Achnanthidiaceae). Notulae Algarum 55: 1 - 4.","Peres, F., Le Cohu, R. & Delmont, D. (2014) Achnanthidium barbei sp. nov. and Achnanthidium costei sp. nov., two new diatoms from French rivers. Diatom Research 29 (4): 387 - 397. https: // doi. org / 10.1080 / 0269249 X. 2014.890956"]}

Achnanthidium acutum L.F.Costa, C.E.Wetzel & Ector sp. nov. (Figs 2–25) Description:—LM: Valves narrowly linear-elliptic, with acutely rounded to very slightly rostrate apices (Figs 2–20); 9.3–21.2 µm long, 2.2–3.2 µm wide. Raphe valve: axial area narrow and linear; central area rounded, sometimes forming a uni- or bilateral rectangular fascia, with no or one shortened stria on both sides of the valve (Figs 2–12). Raphe filiform straight. Transapical striae slightly radiate throughout the entire valve, more spaced in the central area, becoming denser and more strongly radiate towards the apices; 27–30 in 10 µm (Figs 2–12). Rapheless valve: axial area narrow and linear; central area absent, with 1–2 shortened striae on both sides of the valve (Figs 13–20). Transapical striae slightly radiate throughout the entire valve, more spaced in the central area, and becoming denser and more strongly radiate towards the apices; 28–30 in 10 µm (Figs 13–20). SEM: Raphe terminating after the last stria (Figs 21, 22). Central and terminal raphe fissures straight (Figs 21, 22). Striae mainly composed of 3–4 or 4–5 rounded to elongated areolae (Figs 21–25), sometimes slit-like near the valve margin (Figs 21–23). Mantle with one row of slit-like areolae (Figs 21–23). Type:— BRAZIL. São Paulo state: São Paulo, Rio Grande reservoir, epiphyton (Salvinia), 23° 45’ 59.46” S, 46° 30’ 35.7” W, S. Wengrat & D. C.Bicudo, 5th August 2009 (holotype SP-427898! = Fig. 17, isotype: BR-4614). Etymology:— The specific epithet refers to the acutely rounded apices format of the species. Taxonomical remarks:— Concerning the characteristic linear valve shape, A. lineare resembles A. acutum sp. nov. However, A. lineare differs from Brazilian populations mostly by the almost parallel margins and broadly rounded apices in the raphe valves, whereas A. acutum sp. nov. shows narrowly linear-elliptic valves, with acutely rounded to very slightly rostrate apices. Also, the always-rectangular fascia in the central area of the raphe valve in A. lineare contrasts to the nearly rounded central area of A. acutum sp. nov. when observed in LM. Additional remarks include the density of areolae per striae in 10 µm, higher in A. acutum sp. nov. (up to 5) when compared to A. lineare (1– 3). This latter feature can be useful especially regarding the rapheless valve differentiation. The separation of both species was corroborated through morphological analysis between them. The results are presented and discussed in the ‘Morphological patterns in valve shape from EFD analysis’ section. Van de Vijver et al. (2011) analyzed A. lineare type material and described two new species: A. pseudolineare Van de Vijver, Novais & Ector (in Van de Vijver et al. 2011: 186) and A. sublineare Van de Vijver, Jarlman & Ector (in Van de Vijver et al. 2011: 179). Both taxa are described as having a linear outline of the raphe valve. Furthermore, Achnanthidium pseudolineare clearly has a denser number of striae in 10 µm (35–40) compared to A. acutum sp. nov. (27–30). Similarly, A. sublineare has a higher number of striae in 10 µm (33–34), a wider and lanceolate axial area in the rapheless valve, 1–2 areolae per striae and narrower valves (1.5–2.1 µm wide). Besides, this taxon possesses the central area formed by a rectangular fascia in the raphe valve, comparable to those in A. lineare. Achnanthidium petuniabuktianum Pinseel, Van de Vijver & Kopalová (2015: 68) also presents linear valves with rounded apices, but in SEM images, it shows a distinct wide axial area and striae with just 1–2 areolae, differing from A. acutum sp. nov. Also, the terminal raphe fissures are bent to the same side in A. petuniabuktianum while straight in our species. In Brazilian waters, A. brasiliense sp. nov. can co-occurs with A. acutum sp. nov. but can be distinguished by its lanceolate valves with rostrate apices and the linear valves with acutely rounded apices of A. acutum sp. nov. From the Antarctic region, two species closely resemble A. acutum sp. nov. but differ by possessing distinctly protracted and rostrate apices. The first one, A. maritimo-antarcticum Van de Vijver & Kopalová (2014: 6), also has the central area of the rapheless valve in disagreement with A. acutum sp. nov. morphology: it is weakly elliptical, whereas in the Brazilian species a central area is absent. On the other hand, A. indistinctum Van de Vijver & Kopalová (2014: 4) received this name by presenting small frustules (length 8.5–13.0 μm, width 1.8–2.2 μm, Van de Vijver & Kopalová 2014), a feature that distinguish it from our species, since A. acutum sp. nov. has longer and wider valves. In addition, besides the higher stria density (30–35 in 10 μm) than Brazilian taxa, slit-like areolae are apparently never present in A. indistinctum, a feature observed in marginal areolae of some valves in our population. Distribution and ecological information:— Achnanthidium acutum sp. nov. was found in all three habitats (i.e. periphyton, sediment and plankton) and present in 23 % of the quantified samples, being more abundant in periphytic samples (highest abundance: 12 % in SP427898). Due to its wide distribution, the ecological optimum could be calculated. The ecological preference of the species was for neutral pH (optimum of 6.8–7.1), medium to high cond. (optimum of 76.7–167.3 μS∙ cm-1), and meso- to eutrophic waters (TP optimum of 39.0–77.8 μg∙L- 1 and TN optimum of 647.7–1627.9 μg∙L- 1)., Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on pages 194-195, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Van de Vijver, B., Ector, L., Beltrami, M. E., de Haan, M., Falasco, E., Hlubikova, D., Jarlman, A., Kelly, M., Novais, M. H. & Wojtal, A. Z. (2011) A critical analysis of the type material of Achnanthidium lineare W. Sm. (Bacillariophyceae). Algological Studies 136 - 137: 167 - 191. https: // doi. org / 10.1127 / 1864 - 1318 / 2011 / 0136 - 0167","Pinseel, E., Van de Vijver, B. & Kopalova, K. (2015) Achnanthidium petuniabuktianum sp. nov. (Achnanthidiaceae, Bacillariophyta), a new representative of the A. pyrenaicum group from Spitsbergen (Svalbard Archipelago, High Arctic). Phytotaxa 226 (1): 63 - 74. https: // doi. org / 10.11646 / phytotaxa. 226.1.6","Van de Vijver, B. & Kopalova, K. (2014) Four Achnanthidium species (Bacillariophyta) formerly identified as Achnanthidium minutissimum from the Antarctic Region. European Journal of Taxonomy 79: 1 - 19. https: // doi. org / 10.5852 / ejt. 2014.79"]}

Achnanthidium tropicocatenatum G.C.Marquardt, C.E.Wetzel & Ector (Figs 238–275) Morphometric features:— 6.7–18.1 µm long; 2.3–3.1 µm wide; 36–42 striae in 10 µm; striae mainly composed of 4–6 areolae. Taxonomical remarks:— Achnanthidium tropicocatenatum and A. catenatum are similar. In the protologue of the first species, many characters were taken into account to provide the differences between them (e.g. SEM, LM, geometric morphometric analysis, and ecological preferences). Nevertheless, it is possible to distinguish both taxa by the less inflated central portion, fewer capitate apices and higher stria density in A. tropicocatenatum (28–30 striae/10 µm in A. catenatum, Bílý & Marvan 1959). Also, in A. catenatum, the girdle view is distinct, with the valve being strongly curved with the apices sharply pointed. In contrast, in A. tropicocatenatum, the valve is less arched with apices slightly curved (Marquardt et al. 2017). Marquardt et al. (2017) commented about the confusion made with two different populations in Novais et al. (2015), probably joining two different species in one taxon (A. lusitanicum in Novais et al. 2015). The first population from Janeiro de Baixo, Zêzere River (Tejo basin, Portugal), is considered the type material of the species and differs from A. tropicatenatum by its rostrate apices, or broadly rounded ones in smaller specimens. Distribution and ecological information:— The taxon was recently described despite its presence in Brazilian literature being misidentified as A. catenatum. Indeed, in our samples, the species A. tropicocatenatum had the highest frequency of occurrence (61 %). Its ecological optimum was calculated for all habitats. The species showed an ecological preference for slightly acid to neutral (pH optimum of 6.7–6.9), low to medium cond. (optimum of 53.7–94.3 μS∙ cm-1) and mesotrophic waters (TP optimum of 19.8–37.3 μg∙L- 1 and TN optimum of 504.2–665.8 μg∙L- 1). Achnanthidium tropicocatenatum was previously described from oligotrophic conditions in São Paulo state (Marquardt et al. 2017); however, it presented greater tolerance in our study area and was identified from oligo- to eutrophic conditions., Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on page 210, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Bily, J. & Marvan, P. (1959) Achnanthes catenata sp. n. Preslia 31: 34 - 35.","Marquardt, G. C., Costa, L. F., Bicudo, D. C., Bicudo, C. E. M., Blanco, S., Wetzel, C. E. & Ector, L. (2017) Type analysis of Achnanthidium minutissimum and A. catenatum and description of A. tropicocatenatum sp. nov. (Bacillariophyta), a common species in Brazilian reservoirs. Plant Ecology and Evolution 150 (3): 313 - 330. https: // doi. org / 10.5091 / plecevo. 2017.1325","Novais, M. H., Juttner, I., Van de Vijver, B., Morais, M. M., Hoffmann, L. & Ector, L. (2015) Morphological variability within the Achnanthidium minutissimum species complex (Bacillariophyta): comparison between the type material of Achnanthes minutissima and related taxa, and new freshwater Achnanthidium species from Portugal. Phytotaxa 224 (2): 101 - 139. https: // doi. org / 10.11646 / phytotaxa. 224.2.1"]}

Achnanthidium paulistanum L.F.Costa & D.Bicudo sp. nov. (Figs 117–143) Description:— LM: Valves narrowly linear-lanceolate, with subrostrate to rostrate apices (Figs 117–134); 8.4–15.0 µm long, 2.1–2.6 µm wide. Raphe valve: axial area narrow and linear; central area small rounded, almost absent, with 1–2 shortened striae on both sides of the valve, and never forming a fascia (Figs 117–126). Raphe filiform straight. Transapical striae slightly radiate throughout the entire valve, becoming denser and more strongly radiate towards the apices, 30–31 in 10 µm (Figs 117–126). Rapheless valve: axial area narrow and linear, slightly widening towards the central area; central area very small rounded or absent, with 1–2 shortened striae on both sides of the valve (Figs 127–134). Transapical striae slightly radiate throughout the entire valve, becoming denser towards the apices, 30–32 in 10 µm (Figs 127–134). Girdle view rectangularly arched, with apices recurved to the rapheless valve (Figs 135–137). SEM: Raphe terminating right after the last stria (Figs 138–140). Central raphe fissures close, straight and slightly expanded (Figs 138–140). Terminal raphe fissures short, deflected (Figs 138–140). Striae mainly composed of 3–5 rounded to elongated areolae, sometimes slit-like near the valve margin (Figs 138–143). Mantle with one row of slitlike areolae (Figs 139, 140). Type:— BRAZIL. São Paulo state: São Pedro, SP –304, km 127, periphyton from a small lake, A.A.J.Castro & C.E.M.Bicudo, 20th March 1990 (holotype SP-255724! = Fig. 118, isotype: BR-4617). Etymology: —The specific epithet refers to people born in the state of São Paulo (in Portuguese, the “ paulistas ”). Taxonomical remarks:— Achnanthidium paulistanum sp. nov. is characterized by a linear or narrowly lanceolate valve shape, with subrostrate apices. In contrast, A. brasiliense sp. nov. has linear-lanceolate valves and rostrate apices. Notably, the slightly deflected terminal raphe fissures are always present in A. paulistanum sp. nov. valves, a feature that was not observed in A. brasiliense sp. nov. specimens. The central area never forms a fascia and is almost absent in the new species. In this way, the main characters differing in both species are the terminal raphe fissures and the central area shape of the raphid valve. The deflected terminal raphe fissures differentiate the species from others, including A. indistinctum specimens with valve outline very similar to A. paulistanum sp. nov. It also can be distinguished by the girdle view: the Brazilian species has apices recurved to the rapheless valve and mantle striae almost indiscernible in LM, whereas the Antarctic one presents girdle view with apices straight and mantle striae thickened in LM. In valve view, A. indistinctum has slightly higher stria density and slightly narrower valves (1.8–2.2 µm wide, 30–35 striae in 10 µm, Van de Vijver & Kopalová 2014). Achnanthidium maritimo-antarcticum, another Antarctic species, differs by having parallel to slightly convex margins, appearing sometimes undulated, and clearly protracted apices, whereas A. paulistanum sp. nov. has convex to slightly convex margins and apices not clearly differentiate from the main body. In ultrastructure, A. maritimo-antarcticum possesses terminal raphe fissures straight to weakly curved (Van de Vijver & Kopalová 2014). Due to its linear shape, Achnanthidium acutum sp. nov. is morphologically close to this taxon, but A. paulistanum sp. nov. can be narrowly lanceolate. These species also differ with respect to the apices, which are acutely rounded in the first and subrostrate in the latter. Nevertheless, the slightly deflected terminal raphe fissures and the higher stria density in A. paulistanum sp. nov. can be used to separate both taxa. Distribution and ecological information:— The taxon was rare and occurred only in the epiphytic type sample., Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on pages 203-204, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Van de Vijver, B. & Kopalova, K. (2014) Four Achnanthidium species (Bacillariophyta) formerly identified as Achnanthidium minutissimum from the Antarctic Region. European Journal of Taxonomy 79: 1 - 19. https: // doi. org / 10.5852 / ejt. 2014.79"]}

Achnanthidium vandevijveri L.F.Costa, Ector & C.E.Wetzel sp. nov. (Figs 276–316) Description:— LM: Valves 7.8–16.5 µm long, 3.0–3.8 µm wide. Raphe valve: valves linear-lanceolate to rhombiclanceolate, with subrostrate to rostrate apices (Figs 276–291). Axial area narrow and linear, central area absent or small, rounded (Figs 276–291). Raphe filiform and straight. Transapical striae slightly radiate throughout the entire valve, more spaced in the central area, and becoming denser and more strongly radiate towards the apices; 27–34 in 10 µm (Figs 276–291). Rapheless valve: valves linear-lanceolate, with rostrate to subcapitate apices (Figs 292–306). Axial area narrow and linear, slightly widening towards the central area; central area absent to very small rounded (Figs 292–306). Transapical striae slightly radiate throughout the entire valve, becoming denser towards the apices; 30–32 in 10 µm (Figs 292–306). SEM: Raphe prolonged, terminating after the last stria on the border between the valve face and mantle (Figs 307, 308, 311–313). Central raphe fissures close and straight (Figs 307, 308, 311–313). Terminal raphe fissures short, weakly deflected (Figs 307, 308, 311–313). Striae mainly composed of 3–5 rounded to elongated areolae, sometimes slit-like near the valve margin (Figs 307–316). Mantle with one row of slit-like areolae (Figs 307, 309, 314, 315). Type:— BRAZIL. São Paulo state: São Paulo, Garças Lake, periphyton, 23° 38’ 44.4” S, 46° 37’ 29.9” W, P.D.Almeida & D.C.Bicudo, 7th July 2014 (holotype SP-469485! = Fig. 282, isotype: BR-4620). Etymology: —We dedicate this species to Prof. Dr. Bart Van de Vijver (Meise Botanic Garden, Meise, Belgium). Taxonomical remarks: — The different valve outline between the raphe and rapheless valves make the taxon more easily distinguishable from others. The rhombic-lanceolate outline of the raphe valve resembles the taxon to A. eutrophilum. Besides the different rapheless valve outline, A. eutrophilum presents wider valves and slightly lower stria density (3.2–5.8 µm wide, stria density 25–30/10 µm, Hlúbiková et al. 2011). Using SEM it is possible to see other differences such as the prolonged terminal raphe ends after the last stria and the almost never slit-like areolae shape. In contrast, in A. vandevijver sp. nov., the terminal raphe fissures terminate right after the last stria, and the areolae are often slit-like near the margins of the valve. Despite the general similarity, Achnanthidium dolomiticum Cantonati & Lange-Bertalot (2006: 1185) presents its raphe valve with some singularities when compared with A. vandevijveri sp. nov. The Italian species has the central area forming a bilateral narrow fascia, a feature never present in the Brazilian one. In addition, the stria density is slightly higher (33–35 in 10 µm, Cantonati & Lange-Bertalot 2006) than our new species A. vandevijveri sp. nov. From our study area, the rapheless valve of A. vandevijveri sp. nov. is similar to valves of A. lusitanicum. The latter taxon differs mainly by the apices form in the raphe valve. While the rapheless valve has overlapping metric features, they can be distinguished by the visibly rounded central area in A. lusitanicum and the absence or presence of very small, rounded ones in A. vandevijveri sp. nov. Distribution and ecological information:— Achnanthidium vandevijveri sp. nov. was restricted to samples SP-469483 and SP-469485 from Garças Lake, a eutrophic urban lake (Bicudo et al. 2007, 2020) in the metropolitan area of São Paulo. It occurred in plankton, but mainly in periphyton (highest abundance: 15 %). The limnological conditions of the sampling site varied from acid to alkaline (pH 5.8–8.6), cond. was high (307–378 μS∙ cm-1), as were the nutrient concentrations in the environment (TP 97–107.1 μg∙L- 1, TN 1734.2–2757.9 μg∙L- 1)., Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on pages 210-212, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Hlubikova, D., Ector, L. & Hoffmann, L. (2011) Examination of the type material of some diatom species related to Achnanthidium minutissimum (Kutz.) Czarn. (Bacillariophyceae). Algological Studies 136 / 137: 19 - 43. https: // doi. org / 10.1127 / 1864 - 1318 / 2011 / 0136 - 0019","Cantonati, M. & Lange-Bertalot, H. (2006) Achnanthidium dolomiticum sp. nov. (Bacillariophyta) from oligotrophic mountain springs and lakes fed by dolomite aquifers. Journal of Phycology 42 (6): 1184 - 1188. https: // doi. org / 10.1111 / j. 1529 - 8817.2006.00281. x","Bicudo, D. C., Fonseca, B. M., Bini, L. M., Crossetti, L. O., Bicudo, C. E. M. & Araujo-Jesus, T. (2007) Undesirable side-effects of water hyacinth control in a shallow tropical reservoir. Freshwater Biology 52 (6): 1120 - 1133. https: // doi. org / 10.1111 / j. 1365 - 2427.2007.01738. x","Bicudo, D. C., Zanon, J. E., Ferragut, C., Crossetti, L. O., Faustino, S. B. & Bicudo, C. E. M. (2020) Garcas Reservoir trophic state dynamics: a 20 - year synthesis. Hoehnea 47: e 722019. https: // doi. org / 10.1590 / 2236 - 8906 - 72 / 2019"]}

Achnanthidium saprophilum (H.Kobayashi & Mayama) Round & Bukhtiyarova (Figs 215–237) Morphometric features:— 6.0–15.3 µm long; 2.5–3.2 µm wide; 26–32 striae in 10 µm; striae mainly composed of 4–5 areolae. Taxonomical remarks:— The species can be confused with smaller specimens of A. tropicocatenatum, however, they differ by the subcapitate to capitate apices and higher stria density (36–45 in 10 µm) in A. tropicocatenatum. Achnanthidium peetersianum presents small capitate apices and has narrower valves (2.0–2.7 µm) than A. saprophilum. Also, externally terminal raphe fissures are slightly bent to the same side in A. peetersianum, at the same level as the striae on the valve face, whereas in our species external terminal raphe fissures are always straight and terminating after the last striae. Despite displaying different raphid valves with linear-lanceolate to rhombic-lanceolate in A. vandevijveri sp. nov., the rapheless valves present almost the same valve outline as A. saprophilum. However, the valves outline in A. vandevijveri sp. nov. are slightly wider and longer. Achnanthidium acsiae Wojtal, E.Morales, Van de Vijver & Ector (in Wojtal 2011: 226) has similar valve outline and metric features as A. saprophilum, however, the former has the central area of raphe valve often forming a bilateral fascia, a feature never observed in our population. Achnanthidium saprophilum rarely shows a unilateral fascia. Still, the stria density is higher than ours and they are composed of less areolae (28–36 striae in 10 µm, 3–4 areolae per stria, Wojtal et al. 2011). Achnanthidium pseudolineare differs from A. saprophilum by the rapheless valve, presenting linear valves with parallel margins and broadly rounded apices. The stria density is also different between the species, being higher in A. pseudolineare (32–40 in 10 µm, Van de Vijver et al. 2011). Achnanthidium costei Pérès & Le Cohu (in Pérès et al. 2014: 390) also has linear valves with parallel margins, but this outline is characteristic of the raphe valves (Pérès et al. 2014). Its rapheless valves shows another distinct feature: the axial area is wider and lanceolate. Achnanthidium saprophilum has both valves linear-lanceolate with convex margins, and the axial area straight on rapheless valves. Concerning Achnanthidium saprophilum, despite the number of areolae per striae in the isotype being higher (4–7, Hlúbiková et al. 2011) than ours (4–5), the areolae morphology of the valves from our population is variable, including apically elongated areolae, as described for A. saprophilum (Kobayasi & Mayama 1982). Distribution and ecological information:— The species occurred in planktonic, periphytic and surface sediment assemblages in low abundance (, Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on pages 208-210, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Wojtal, A. Z., Ector, L., Van de Vijver, B., Morales, E. A., Blanco, S., Piatek, J. & Smieja, A. (2011) The Achnanthidium minutissimum complex (Bacillariophyceae) in southern Poland. Algological Studies 136 - 137: 211 - 238. https: // doi. org / 10.1127 / 1864 - 1318 / 2011 / 0136 - 0211","Van de Vijver, B., Ector, L., Beltrami, M. E., de Haan, M., Falasco, E., Hlubikova, D., Jarlman, A., Kelly, M., Novais, M. H. & Wojtal, A. Z. (2011) A critical analysis of the type material of Achnanthidium lineare W. Sm. (Bacillariophyceae). Algological Studies 136 - 137: 167 - 191. https: // doi. org / 10.1127 / 1864 - 1318 / 2011 / 0136 - 0167","Peres, F., Le Cohu, R. & Delmont, D. (2014) Achnanthidium barbei sp. nov. and Achnanthidium costei sp. nov., two new diatoms from French rivers. Diatom Research 29 (4): 387 - 397. https: // doi. org / 10.1080 / 0269249 X. 2014.890956","Hlubikova, D., Ector, L. & Hoffmann, L. (2011) Examination of the type material of some diatom species related to Achnanthidium minutissimum (Kutz.) Czarn. (Bacillariophyceae). Algological Studies 136 / 137: 19 - 43. https: // doi. org / 10.1127 / 1864 - 1318 / 2011 / 0136 - 0019","Kobayasi, H. & Mayama, S. (1982) Most pollution-tolerant diatoms of severely polluted rivers in the vicinity of Tokyo. Japanese Journal of Phycology 30: 188 - 196."]}

Achnanthidium ritae L.F.Costa sp. nov. (Figs 194–214) Description:— LM: Valves linear-elliptic, with non-protracted, broadly rounded apices (Figs 194–210); 5.3–10.3 µm long, 2.5–2.9 µm wide. Raphe valve: axial area narrow and linear, central area absent or small rounded, sometimes with one shortened stria on both sides of the valve (Figs 194–201). Raphe filiform and straight. Transapical striae slightly radiate throughout the entire valve, more spaced in the central area (Figs 194–201); 28–30 in 10 µm. Rapheless valve: axial area narrow and linear, slightly widening towards the central area; central area absent or narrow lanceolate (Figs 202–210). Transapical striae slightly radiate throughout the entire valve, more spaced in the central area; 26–28 in 10 µm (Figs 202–210). SEM: Raphe prolonged, terminating after the last stria (Fig. 211). Central raphe fissures close, straight and droplike expanded (Fig. 211). Terminal raphe fissures straight (Fig. 211). Striae mainly composed of 4–6 rounded to almost squared or elongated areolae (Figs 211–214). Mantle with one row of slit-like areolae (Figs 211–214). Type:— BRAZIL. São Paulo state: São Paulo, Billings Complex, Taquacetuba branch, epilithon, 23° 48’ 44.1” S, 46° 37’ 51.24” W, S.Wengrat & D.C.Bicudo, 7th August 2009 (holotype SP-427904! = Fig. 205, isotype: BR-4619). Etymology:— This species is dedicated to Rita Franco. Taxonomical remarks:— Achnanthidium duriense Novais & Ector is the most similar species, however, it differs by having rapheless valves clearly lanceolate, and also by the higher stria density (35 in 10 µm, Novais et al. 2015). Achnanthidium straubianum (Lange-Bertalot) Lange-Bertalot (1999: 273) presented wider valves in the protologue (3.5–4 µm wide, Lange-Bertalot & Metzeltin 1996), compared to the isotype that has narrower valves (2.6–3.5 µm, Hlúbiková et al. 2011). However, even in the isotype illustrations it is possible to observe wider and shorter valves (ratio length/width 2.0–2.6, measured from the Figs 73–103 in Hlúbiková et al. 2011) than the species described herein (2.2–3.9). Hlúbiková et al. (2011) stated the combination of length, width and striation pattern as a reliable criterion to separate A. straubianum from similar species. Another taxon resembling A. ritae sp. nov. is A. nanum (F.Meister) Novais & Jüttner (in Novais et al. 2015: 121), a species described from Switzerland (Meister 1935). Achnanthidium nanum presents a different valve outline in the illustrations of the protologue and type material reevaluated in Novais et al. (2015). It also has linear-lanceolate valves differing from the linear-elliptic valves of A. ritae sp. nov. Also, the species present different areolae shapes and the central area of our specimens is often absent while it is clearly visible in A. nanum. Two species recently described from Korea, Achnanthidium ovale M.Miao & B.-H.Kim (in Miao et al. 2020: 5) and Achnanthidium cavitatum M.Miao & B.-H.Kim (in Miao et al. 2020: 7), also can be compared to the Brazilian species. Achnanthidium ovale has a more elliptic valve outline, wider valves (3.8–4.1 µm) and a greater stria density (30–35 in 10 µm). The ultrastructural differences, such as the terminal raphe fissures strongly bent to the same side in the Korean taxon, are another notable feature (Miao et al. 2020). Achnanthidium cavitatum is similar in that it has linear-elliptic valves; however, the main difference from A. ritae sp. nov. is the wider axial area observed in the rapheless valve (Miao et al. 2020). Achnanthidium cavitatum also has slightly wider valves (3.0–3.5 µm, Miao et al. 2020) than our population. Furthermore, Achnanthidium rivulare Potapova & Ponader (2004: 36) and A. crassum (Hustedt) Ponader & Potapova (in Potapova & Ponader 2004: 38) differ from A. ritae sp. nov. in their linear-lanceolate axial area in the raphe valve, unilaterally deflected terminal raphe fissures and wider valves (2.6–4.4 µm and 3–4.5 µm respectively, Potapova & Ponader 2004). Distribution and ecological information:— Achnanthidium ritae sp. nov. was found in 8 % of the counted samples, mainly occurring in periphytic samples (highest abundance: 14 % in SP-427904) with an ecological preference for alkaline (pH optimum of 7.9), high cond. (optimum of 182.4 μS∙ cm-1) and mesotrophic water conditions (TP optimum of 41.1 μg∙L- 1 and TN optimum 1306.2 μg∙L- 1). It also presented a wide tolerance and was found to occur in oligo- to eutrophic waters., Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on pages 207-208, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Novais, M. H., Juttner, I., Van de Vijver, B., Morais, M. M., Hoffmann, L. & Ector, L. (2015) Morphological variability within the Achnanthidium minutissimum species complex (Bacillariophyta): comparison between the type material of Achnanthes minutissima and related taxa, and new freshwater Achnanthidium species from Portugal. Phytotaxa 224 (2): 101 - 139. https: // doi. org / 10.11646 / phytotaxa. 224.2.1","Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus Achnanthes Bory (sensu lato). In: Lange-Bertalot, H. (Ed.), Iconographia Diatomologica. Annotated Diatom Micrographs. Vol. 6. Phytogeography - Diversity - Taxonomy. Koeltz Scientific Books, Konigstein, Germany, pp. 276 - 289.","Lange-Bertalot, H. & Metzeltin, D. (1996) Oligotrophie-Indikatoren. 800 Taxa reprasentativ fur drei diverse Seen-Typen. Kalkreich - Oligodysroph - Schwach gepuffertes Weichwasser [Indicators of oligotrophy. 800 taxa representative of three ecologically distinct lake types. Carbonate buffered - Oligodystrophic - Weakly buffered soft water]. Iconographia Diatomologica 2: 1 - 390.","Hlubikova, D., Ector, L. & Hoffmann, L. (2011) Examination of the type material of some diatom species related to Achnanthidium minutissimum (Kutz.) Czarn. (Bacillariophyceae). Algological Studies 136 / 137: 19 - 43. https: // doi. org / 10.1127 / 1864 - 1318 / 2011 / 0136 - 0019","Meister, F. (1935) Seltene und neue Kieselalgen. Bericht der Schweizerischen Botanischen Gesellschaft 44: 87 - 108.","Miao, M., Li, Z., Hwang, E. - A., Kim, H. - K., Lee, H. & Kim, B. - H. (2020) Two new benthic diatoms of the genus Achnanthidium (Bacillariophyceae) from the Hangang River, Korea. Diversity 12 (7): 285. https: // doi. org / 10.3390 / d 12070285","Potapova, M. G. & Ponader, K. C. (2004) Two common North American diatoms, Achnanthidium rivulare sp. nov. and A. deflexum (Reimer) Kingston: morphology, ecology and comparison with related species. Diatom Research 19 (1): 33 - 57. https: // doi. org / 10.1080 / 0269249 X. 2004.9705606"]}

Achnanthidium sp. (Figs 317–327) LM observations:— Valves linear-elliptic to linear-lanceolate, with broadly rounded apices to subrostrate (Figs 317– 327); 7.4–11.6 µm long, 3.5–4.1 µm wide. Raphe valve: axial area narrow and linear, central area small rounded, with 1–2 shortened striae on both sides of the valve (Figs 317–321). Raphe filiform straight. Transapical striae slightly radiate throughout the entire valve, becoming denser and strongly radiate towards the apices; 24–28 in 10 µm (Figs 317–321). Rapheless valve: axial area narrow and linear, widening towards the central area, central area absent or lanceolate (Figs 322–327). Transapical striae radiate throughout the entire valve, becoming denser and strongly radiate towards the apices; 23–27 in 10 µm (Figs 322–327). Taxonomical remarks:— Achnanthidium modestiformis (Lange-Bertalot) Van de Vijver (in Van de Vijver et al. 2002: 17) presents similar morphometric features (12–17 µm long, 3.5–4 µm wide, stria density 24–25/10 µm, as Achnanthes modesta Manguin (in Bourrelly & Manguin 1954: 22). However, the Brazilian population has broadly rounded to rostrate apices, whereas they are more capitate in A. modestiformis. Moreover, Achnanthidium sp. has shorter valves. Another similar specimen cited in Brazilian literature is Achnanthes acares M.H. Hohn & Hellerman (1963: 273) (Schneck et al. 2008). The illustrations presented by Hohn & Hellerman (1963) concerning this taxon show a different central area, elliptical in the raphe valve and coarse striae resembling Planothidium. Krammer & Lange-Bertalot (1991) illustrated the holotype of this species using LM, however, they only showed the raphe valves of the specimens, which probably do not correspond to a monoraphid taxon. Additionally, another Brazilian population resembled ours, but it was not identified at the species level (Santos et al. 2011, Figs 21–24, as “ Achnanthidium sp. ”). More studies are necessary concerning the identity of this taxon. Distribution and ecological information:— Achnanthidium sp. was rare (occurrence of, Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on pages 214-215, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Van de Vijver, B., Frenot, Y. & Beyens, L. (2002) Freshwater diatoms from Ile de la Possession (Crozet Archipelago, Subantarctica). Bibliotheca Diatomologica 46: 1 - 412.","Bourrelly, P. & Manguin, E. (1954) Contribution a la flore algale d'eau douce des Iles Kerguelen. Memoires de l'Institut Scientifique de Madagascar, series B 5: 5 - 58.","Hohn, M. H. & Hellerman, J. (1963) The taxonomy and structure of diatom populations from three Eastern North American rivers using three sampling methods. Transactions of the American Microscopical Society 82 (3): 250 - 329. https: // doi. org / 10.2307 / 3223932","Schneck, F., Torgan, L. C. & Schwarzbold, A. (2008) Diatomaceas epiliticas em riacho de altitude no sul do Brasil. Rodriguesia 59 (2): 325 - 338. https: // doi. org / 10.1590 / 2175 - 7860200859205","Krammer, K. & Lange-Bertalot, H. (1991) Bacillariophyceae 4. Teil: Achnanthaceae, Kritische Erganzungen zu Navicula (Lineolatae) und Gomphonema. Gesamtliteraturverzeichnis Teil 1 - 4. In: Ettl, H., Gartner, G., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.) Susswasserflora von Mitteleuropa Vol. 2 / 4. Gustav Fischer Verlag, Stuttgart-Jena, pp. 1 - 437.","Santos, E. M., Tremarin, P. I. & Ludwig, T. A. V. (2011) Diatomaceas perifiticas em Potamogeton polygonus Cham. & Schltdl.: citacoes pioneiras para o estado do Parana [Periphytic diatoms on Potamogeton polygonus Cham. & Schltdl.: first records from Parana State]. Biota Neotropica 11 (3): 303 - 315. https: // doi. org / 10.1590 / S 1676 - 06032011000300025"]}

Achnanthidium parvicapitatum L.F.Costa, Ector & C.E.Wetzel sp. nov. (Figs 100–116) Description:— LM: Valves linear-lanceolate, with subtle shoulders and subcapitate to small capitate apices (Figs 100– 111); 18.2–22.7 µm long, 2.7–3.0 µm wide. Raphe valve: axial area narrow and linear, central area rounded, with 2–4 shortened striae on both sides of the valve, rarely forming a rectangular fascia (Figs 100–105). Raphe filiform straight. Transapical striae slightly radiate throughout the entire valve, more spaced in the central area, and becoming denser and more strongly radiate towards the apices (Figs 100–105); 29–33 in 10 µm. Rapheless valve: axial area narrow and linear, widening towards the central area; central area absent or narrow lanceolate, with 1–2 shortened striae on both sides of the valve (Figs 106–111). Transapical striae slightly radiate throughout the entire valve, more spaced in the central area, and becoming denser towards the apices; 28–32 in 10 µm. Girdle view rectangularly arched, with pointed apices recurved to the rapheless valve (Fig. 112). SEM: Raphe prolonged after the striae, terminating on the border between the valve face and mantle (Fig. 113). Central and terminal raphe fissures straight (Fig. 113). Striae mainly composed of 3–4 or 4–5 rounded to elongated areolae, sometimes slit-like near the valve margin (Figs 113, 115). Mantle with one row of slit-like areolae (Fig. 113). Presence of two small punctuations, spaced and apically arranged on central area of rapheless valve of some longer valves (Fig. 115). Type:— BRAZIL. São Paulo state: Votorantim, Santa Helena reservoir, epilithon, 23º 34’ 58.56” S, 47º 25’ 50.52” W, E.C. R. Bartozek & D.C.Bicudo, 27th February 2014 (holotype SP-469524! = Fig. 108, isotype: BR-4616). Etymology:— The specific epithet refers to the shape of the apices, which are small and capitate. Taxonomical remarks:— Achnanthidium sieminskae Witkowski, Kulikovskiy & Riaux-Gobin (2012: 65) described from marine environments of the Kerguelen Archipelago, Austral Islands (Witkowski et al. 2012) resemble our population. The Antarctic taxon has linear to narrowly linear-lanceolate valves with almost parallel to slightly convex margins (Van de Vijver & Kopalová 2014), whereas A. parvicapitatum sp. nov. has more lanceolate valves with clearly convex margins, with the central portion evidently larger than the constriction before the apices, and sometimes larger than the apices. The apices in A. sieminskae can also be rostrate (Van de Vijver & Kopalová 2014), differing from our populations. Achnanthidium caledonicum (Lange-Bertalot) Lange-Bertalot (1999: 277) can be confused with A. parvicapitatum sp. nov. The main difference between these two species is the broadly capitate apices in A. caledonicum, while the Brazilian species present small capitate to subcapitate specimens. Another difference is that the valves of A. caledonicum are linear with parallel margins or sometimes inflated just at the centre, while A. parvicapitatum sp. nov. is linear-lanceolate and narrower. Previously, one Austrian specimen, in a mixed population, closely resembling A. parvicapitatum sp. nov. was illustrated in Lange-Bertalot & Krammer (1989, pl. 55, Fig. 4) and identified as Achnanthes minutissima var. scotica (J.R.Carter) Lange-Bertalot (in Lange-Bertalot & Krammer 1989: 106; currently considered a synonym of Achnanthidium caledonicum). Specimens incorrectly identified as A. caledonicum are very similar (Krammer & Lange-Bertalot 2004, pl. 34, Figs 4–6) and an investigation of those specimens is currently being carried out. Furthermore, similar German specimens were also identified as Achnanthidium cf. caledonicum (pl. 24, Figs 58–60 in Lange-Bertalot et al. 2017). Achnanthidium neomicrocephalum Lange-Bertalot & F.Staab (in Krammer & Lange-Bertalot 2004: 431) bears some similarities with A. parvicapitatum sp. nov., such as linear-lanceolate valves with capitate to subcapitate apices. Its slender valve shape with longer, narrower valves (22–38 µm long, 2.5–2.8 µm wide, Krammer & Lange-Bertalot 2004) allows their separation, even though there are some overlaps in size ranges reported (21.6–25.3 μm long, 2.5–2.8 μm wide, by Silva-Lehmkuhl et al. 2019). Another distinction between the taxa is the subtle shoulders observed in the Brazilian populations but not present in A. neomicrocephalum. Recently described from China, Achnanthidium longissimum P.Yu, Q. -M.You & Kociolek (in Yu et al. 2018: 340) was compared in its protologue to A. caledonicum and A. neomicrocephalum. Despite the similar valve outline to A. parvicapitatum sp. nov., A. longissimum has capitate apices, and the raphe’s terminal fissures are strongly bent towards the same side of the valve. This feature is clearly visible in LM images. Achnanthidium longissimum also has larger valves and a reduced stria density (36–48 μm long, 4.0–4.5 μm wide, 22–25 striae in 10 μm, Yu et al. 2018) when compared to the new Brazilian taxon. Another similar species to A. parvicapitatum sp. nov. is Achnanthidium digitatum Pinseel, Vanormelingen, P.B.Hamilton & Van de Vijver (in Pinseel et al. 2017: 271). However, A. digitatum has smaller, narrower valves and a higher stria density (8.6–19.1 μm long, 1.8–2.3 μm wide, 31–36 striae in 10 µm, Pinseel et al. 2017). Additionally, the valves of A. digitatum are more linear, with margins almost parallel, and the striae are mostly composed of two areolae, an observation that is different from the population described here. In our study area, A. parvicapitatum sp. nov. co-occurred with two taxa that are sometimes difficult to separate using LM: A. brasiliense sp. nov. and A. tropicocatenatum. In general, smaller specimens are difficult to discern, however, A. parvicapitatum sp. nov. is usually slender and has less lanceolate valve margins than A. brasiliense sp. nov. They also have slightly distinct apices, while the latter taxon presents more rostrate than subcapitate apices. Concerning A. tropicocatenatum, it is smaller and presents visibly inflated valves in the median portion. The girdle view is also slightly arched, but the apices in A. tropicocatenatum are more strongly and sharply recurved to the rapheless valve. Distribution and ecological information:— Achnanthidium parvicapitatum sp. nov. was distributed in all the habitats, occurring in 20 % of the counted samples (highest abundance: 36 % in SP-428935). In all the communities, the species showed ecological preferences for slightly acid (pH optimum of 6.6–6.8), low to medium cond. (optimum of 56–74 μS∙ cm-1), and oligo- to mesotrophic water conditions (TP optimum of 14.1–22.5 μg∙L- 1 and TN optimum of 321.4–468.2 μg∙L- 1)., Published as part of Costa, Lívia F., Wetzel, Carlos E., Maquardt, Gisele C., Zanon, Jaques E., Ector, Luc & Bicudo, Denise C., 2022, Taxonomy and ecology of Achnanthidium (Bacillariophyta, Achnanthidiaceae) from southeastern Brazil with the description of six new species, pp. 187-223 in Phytotaxa 575 (3) on pages 201-202, DOI: 10.11646/phytotaxa.575.3.1, http://zenodo.org/record/7431242, {"references":["Witkowski, A., Kulikovskiy, M. & Riaux-Gobin, C. (2012) Achnanthidium sieminskae, a new diatom species from the Kerguelen Archipelago (Austral Islands). In: Wolowski, K., Kaczmarska, I., Ehrman, J. M. & Wojtal, A. Z. (Eds.) Current Advances in Algal Taxonomy and its Applications. W. Szafer Institute of Botany, Polish Academy of Sciences, Krakow, pp. 61 - 68.","Van de Vijver, B. & Kopalova, K. (2014) Four Achnanthidium species (Bacillariophyta) formerly identified as Achnanthidium minutissimum from the Antarctic Region. European Journal of Taxonomy 79: 1 - 19. https: // doi. org / 10.5852 / ejt. 2014.79","Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus Achnanthes Bory (sensu lato). In: Lange-Bertalot, H. (Ed.), Iconographia Diatomologica. Annotated Diatom Micrographs. Vol. 6. Phytogeography - Diversity - Taxonomy. Koeltz Scientific Books, Konigstein, Germany, pp. 276 - 289.","Lange-Bertalot, H. & Krammer, K. (1989) Achnanthes eine Monographie der Gattung mit Definition der Gattung Cocconeis und Nachtragen zu den Naviculaceae. Bibliotheca Diatomologica 18: 1 - 393.","Krammer, K. & Lange-Bertalot, H. (2004) Bacillariophyceae 4. Teil: Achnanthaceae, Kritische Erganzungen zu Achnanthes s. l., Navicula s. str., Gomphonema. Gesamtliteraturverzeichnis Teil 1 - 4. In: Ettl, H., Gartner, G., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.) Susswasserflora von Mitteleuropa Vol. 2 / 4. Spektrum Akademischer Verlag, Heidelberg-Berlin, pp. 1 - 468.","Lange-Bertalot, H., Hofmann, G., Werum, M. & Cantonati, M. (2017) Freshwater benthic diatoms of Central Europe: over 800 common species used in ecological assessment. English edition with updated taxonomy and added species. In: Cantonati, M., Kelly, M. G. & Lange-Bertalot, H. (Eds.) Koeltz Botanical Books, Schmitten-Oberreifenberg, pp. 1 - 942.","Silva-Lehmkuhl, A. M., Tremarin, P. I., Vercellino, I. S. & Ludwig, T. A. V. (2019) Periphytic diatoms from an oligotrophic lentic system, Piraquara I reservoir, Parana state, Brazil. Biota Neotropica 19 (2): e 20180568. https: // doi. org / 10.1590 / 1676 - 0611 - bn- 2018 - 0568","Yu, P., Kociolek, J. P., You, Q. & Wang, Q. (2018) Achnanthidium longissimum sp. nov. (Bacillariophyta), a new diatom species from Jiuzhai Valley, Southwestern China. Diatom Research 33 (3): 339 - 348. https: // doi. org / 10.1080 / 0269249 X. 2018.1545704","Pinseel, E., Vanormelingen, P., Hamilton, P. B., Vyverman, W., Van de Vijver, B. & Kopalova, K. (2017) Molecular and morphological characterization of the Achnanthidium minutissimum complex (Bacillariophyta) in Petuniabukta (Spitsbergen, High Arctic) including the description of A. digitatum sp. nov. European Journal of Phycology 52 (3): 264 - 280. https: // doi. org / 10.1080 / 09670262.2017.1283540"]}

Achnanthidium minutissimum (Kütz.) Czarn. (Fig. 14) Memoirs of the California Academy of Sciences 17: 157 (Czarnecki 1994). — Basionym: Achnanthes minutissima Kütz., Linnaea 8 (5): 578, pl. 16, fig. 54 (Kützing 1833); Kützing, 50, pl. 4, fig. 54 (Kützing 1834); Kützing, Dec. VIII, no. 75 (Kützing 1834), in Kützing, Algarum Aquae Dulcis Germanicum, Decades I-XVI, numbers 1-160. Halis Saxonum, 1833-1836. DESCRIPTION LM (Fig. 14 A-AW) Frustules slightly arched, with convex RL, concave RV. Valves linear-lanceolate. Margins tapering gradually towards short protracted rounded, rostrate poles. Valve dimensions (n = 46): length 8.5-15 µm, width 2.5-3.5 µm. Central area on raphe valve varies from small rounded to a narrow rectangular fascia on one or both sides. Striae more widely spaced in valve centre. Raphe filiform, straight, central pores slightly widened, terminating close to margin of central area. Central area on rapheless valve indistinct or narrow elliptical. Axial area narrow linear on both valves, slightly widening towards valve centre. Striae radiate throughout on both valves, 30-35 in 10 µm (RV and RL), becoming denser at poles., Published as part of Jüttner, Ingrid, Hamilton, Paul B., Wetzel, Carlos E., De, Bart Van, Vijver, King, Lydia, Kelly, Martyn G., Williams, David M. & Ector, Luc, 2022, A study of the morphology and distribution of four Achnanthidium Kütz. species (Bacillariophyta), implications for ecological status assessment, and description of two new European species, pp. 147-176 in Cryptogamie, Algologie 20 (10) on page 155, DOI: 10.5252/cryptogamie-algologie2022v43a10, http://zenodo.org/record/7819378, {"references":["CZARNECKI D. B. 1994. - The freshwater diatom culture collection at Loras College, Dubuque, Iowa, in KOCIOLEK J. P. (ed.), Proceedings of the 11 th International Diatom Symposium, San Francisco, 12 - 17 August 1990. Memoirs of the California Academy of Sciences 17: 155 - 174.","KUTZING F. T. 1833. - Synopsis Diatomacearum oder Versuch einer systematischen Zusammenstellung der Diatomeen. Linnaea 8 (5): 529 - 620."]}

Achnanthidium neomicrocephalum Lange-Bert. & F.Staab (Figs 9-13) Süsswasserflora von Mitteleuropa, Bacillariophyceae. 4. Teil Achnanthaceae: 431, pl. 89, figs 1-13 (Krammer & Lange-Bertalot 2004). DESCRIPTION LM (Fig. 9 A-DZ) Frustules slightly arched, with convex RL, concave RV.Valves linear-lanceolate. Margins slightly tapering towards small protracted, capitate poles. Valve margins slightly inflated in valve centre, sometimes more strongly on one side. Valve dimensions (n = 31): length 12-30.5 µm, width at valve centre 2-2.5 µm. On RV, central area small rounded, bordered by 1-2 slightly shortened, more widely spaced striae on each side, or small transverse fascia. Raphe filiform, straight, central pores terminating close to margin of central area. Central area on rapheless valve indistinct. Axial area narrow, linear on both valves, slightly widening towards valve centre. Striae radiate throughout on both valves, 30-32 in 10 µm (RV and RL). SEM (Figs 10 A-H; 11A-F; 12A-H; 13A-D) Raphe located on slightly raised sternum, terminal raphe fissures straight terminating at valve/mantle junction. Internally, central raphe endings shortly deflected to opposite sides. Striae composed of 2-3 areolae (RV and RL). Areolae round or oval adjacent to axial area, sometimes slit-like adjacent to valve margin. Row of transapically elongated areolae on mantle separated from areolae on valve face by hyaline area.

Achnanthidium lacuslustense sp. nov. (Figs 17; 18) HOLOTYPE. — Germany. Lustsee, 14.IV.2013, I. Jüttner (holo-, NMW [NMW.C.2013.010.2013]; iso-, BM, BR, CANA). TYPE LOCALITY. — Germany. Upper Bavaria, Osterseen area, Lustsee, 47°48’33.509”N, 11°17’36.959”E. HABITAT. — Epiphytic and epipsammic in lake littoral. ETYMOLOGY. — The species was named after the location where it was found, the Lustsee in Upper Bavaria, Germany. REGISTRATION. — http://phycobank.org/103380 DESCRIPTION LM (Fig. 17 A-M) Frustules with strongly concave RV and convex RL with recurved poles.Valves lanceolate,margins tapering gradually towards large capitate poles.Width of poles slightly less or as wide as the maximum width at valve centre. Valve dimensions (n = 14): length 15.5-29.0 µm, width at valve centre 3-4 µm.Central area on RV a moderately broad fascia.Raphe filiform, straight.Central pores slightly expanded, terminating at margin of central area.Central area on RL rectangular, bordered by 2 short striae on each side. Axial area narrow linear on both valves. Striae radiate throughout on both valves, 28-30 in 10 µm (RV), 30 in 10 µm (RL). SEM (Fig. 18 A-H) Raphe located on raised sternum, central raphe endings slightly expanded, tear drop-shaped, terminal raphe fissures straight with tear drop-shaped ends, terminating at valve/ mantle junction. Internally, central raphe endings very slightly deflected to opposite sides, terminating on side of central nod - ule, terminal raphe endings form small helictoglossae. Striae straight on RV, composed of 3-4, rarely 2, areolae. Areolae round adjacent to axial area and at poles, others often slit-like. On RL striae straight, slightly curved at poles, composed of 3-4, rarely 2 or 5, areolae. Areolae mostly round adjacent to axial area, elsewhere often transapically elongate, internally occluded by individual hymenes. A row of transapically elongated areolae on mantle separated from areolae on valve face by a hyaline area.

Achnanthidium tirolense sp. nov. (Figs 15; 16) HOLOTYPE. — Austria. Plansee, 18.IV.2019, I. Jüttner (holo-, NMW [NMW.C.2021.06.2019]; iso-, BM, BR, CANA). TYPE LOCALITY. — Austria. Tyrol, Kleiner Plansee, Plansee, 47°28’34.756”N, 10°46’50.861”E. HABITAT. — Epiphytic and epilithic in lake littoral. ETYMOLOGY. — The species was named after the region where it was found, Tyrol, Austria. REGISTRATION. — http://phycobank.org/103379 DESCRIPTION LM (Fig. 15 A-AG) Valves rhombic-lanceolate with slightly inflated valve centre. Margins tapering gradually towards long protracted, broadly rounded, rostrate poles. Valve dimensions (n = 25): length 14-23.5 µm, width at valve centre 3-4 µm. Central area on RV an acute-angled fascia. Raphe filiform, straight. Central pores slightly expanded, distantly placed at margin of central area. Central area on RL narrow lanceolate, sometimes a narrow acute-angled fascia on one or both sides formed by more widely spaced central striae. Axial area narrow linear on both valves. Striae radiate throughout on both valves, 28-30 in 10 µm (RV and RL). SEM (Fig. 16 A-F) Raphe located on slightly raised sternum, central raphe endings small, round, terminal raphe fissures straight with tear drop-shaped ends, terminating at valve/mantle junction. Internally, central raphe endings slightly deflected to opposite sides, terminal raphe endings form small helictoglossae. Striae straight or slightly curved, on RV composed of 3-5 areolae, on RL composed of 2-5 areolae. Areolae round, those adjacent to valve margin round or slit-like. One row of transapically elongated areolae on mantle separated from areolae on valve face by a hyaline area.

Jüttner, Ingrid, Hamilton, Paul B., Wetzel, Carlos E., De, Bart Van, Vijver, King, Lydia, Kelly, Martyn G., Williams, David M., Ector, Luc (2022): A study of the morphology and distribution of four Achnanthidium Kütz. species (Bacillariophyta), implications for ecological status assessment, and description of two new European species. Cryptogamie, Algologie 20 (10): 147-176, DOI: 10.5252/cryptogamie-algologie2022v43a10

Achnanthidium caledonicum (Lange-Bert.) Lange-Bert. (Figs 2-4) Iconographia Diatomologica 6: 270-283 (Lange-Bertalot 1999). — Achnanthes microcephala f. scotica J.R.Carter in Carter & Bailey- Watts, Nova Hedwigia 33: 534, pl. 1, fig. 31 (Carter & Bailey-Watts 1981). — Achnanthes minutissima var. scotica (J.R.Carter) Lange- Bert.in Lange-Bertalot & Krammer, Bibliotheca Diatomologica 18: 106, pl. 55, figs 4-12, pl. 57, fig. 11, pl. 67, figs 35-56 (Lange-Bertalot & Krammer 1989). — Achnanthes scotica (J.R.Carter) Lange-Bert., Bibliotheca Diatomologica 27: 8 (Lange-Bertalot 1993), nom. illeg., non Achnanthes scotica Flower & V.J.Jones, Diatom Research 4: 228, figs 1-7, 42-53 (Flower & Jones 1989). — Achnanthidium minutissimum var. scoticum (J.R.Carter) H.Cremer in Cremer & Wagner, Polar Biology 26: 108 (Cremer & Wagner 2003). — Basionym: Achnanthes caledonica Lange-Bert. in Lange-Bertalot & Moser, Bibliotheca Diatomologica 29: 95 (Lange-Bertalot & Moser 1994). DESCRIPTION LM (Fig. 2 A-AN) Frustules moderately arched, with convex rapheless valves, concave raphe valves, and recurved poles. Valves linear with large, subcapitate to capitate poles, the latter sometimes wider than the maximum valve width at valve centre. Valve margins tapering slightly towards a small constriction before poles. At valve centre, margins slightly inflated, sometimes unilaterally, or straight. Valve dimensions (n = 20): length 17.5-37.5 µm, width at valve centre: 3.0-3.5 µm. On raphe valve (RV), shape of central area variable, either a small transverse fascia, or oval to round, bordered by one or several slightly shortened striae. Raphe filiform, straight, central pores hardly widened, distantly placed at margin of central area. Central area on rapheless valve (RL) narrow lanceolate. Axial area narrow linear on both valves. Striae radiate throughout on both valves, more distantly placed in valve centre, 30-32 in 10 µm. SEM (Figs 3 A-F; 4A-D) Raphe located on slightly raised sternum, terminal fissures straight terminating at valve/mantle junction. Internally, central raphe endings shortly deflected to opposite sides, terminal raphe endings form small helictoglossae. Striae composed of 2-4 (RV) and 2-5 (RL) areolae. Areolae round or oval, areolae adjacent to valve margin slit-like. Row of transapically elongated areolae on mantle separated from areolae on valve face by hyaline area. On the type slide (lecto-, BM[BM 94890], ex J.R. Carter 3665), the species is common, but many specimens are positioned in girdle view. The central area is often a fascia, as mentioned by Carter (Carter & Bailey-Watts 1981), but sometimes less conspicuous, irregular, and formed by more widely spaced central striae., Published as part of Jüttner, Ingrid, Hamilton, Paul B., Wetzel, Carlos E., De, Bart Van, Vijver, King, Lydia, Kelly, Martyn G., Williams, David M. & Ector, Luc, 2022, A study of the morphology and distribution of four Achnanthidium Kütz. species (Bacillariophyta), implications for ecological status assessment, and description of two new European species, pp. 147-176 in Cryptogamie, Algologie 20 (10) on pages 152-153, DOI: 10.5252/cryptogamie-algologie2022v43a10, http://zenodo.org/record/7819378, {"references":["FLOWER R. J. & JONES V. J. 1989. - Taxonomic descriptions and occurrences of new Achnanthes taxa in acid lakes in the U. K. Diatom Research 4 (2): 227 - 239 https: // doi. org / 10.1080 / 0269 249 X. 1989.9705072","CREMER H. & WAGNER B. 2003. - The diatom flora in the ultraoligotrophic Lake El'gygytgyn, Chukotka. Polar Biology 26: 105 - 114. https: // doi. org / 10.1007 / s 00300 - 002 - 0445 - 0"]}

Based on marine benthic diatoms collected at Potter Cove (Western Antarctic Peninsula), we present a detailed study, using both light and electron microscopy, of the morphology of Campyloneis frenguelliae, a species recently transferred from Cocconeis. Ultrastructural observations revealed a combination of new and unusual features within the Achnanthales: a raphe valve with different areolation patterns, a hollow valvocopula with no apparent fimbriae, and a sternum valve externally ornamented by an embossed structure, areolae occluded by hymenes mostly supported by one short peg, and multiple marginal pores that open internally into shallow valve depressions. In view of these unique set of features, we describe Australoneis gen. nov. to include Australoneis frenguelliae comb. nov. and designate a sample from Potter Cove as epitype of the latter. The main characteristics of the new genus are compared to those of its closely allied Cocconeis, Campyloneis, Xenococconeis and Amphicocconeis.

Platessa arborea sp. nov. new monoraphid diatom species is described from the tree moss habitat of India’s Sikkim state from the Eastern Himalayan biodiversity hotspot. This new species was described based on light and scanning electron micrographs and compared to morphologically similar taxa. Platessa arborea seems to have an affinity for the aerial habitat and has certain unique morphological features distinct from all the other Platessa species, such as its narrowly rounded apices, wide axial area, and the presence of predominantly uniseriate striae with unusually thick striae density. In India, there have been previous reports of some species from the genera Achnanthes and Cocconeis, which have been eventually transferred to the genus Platessa. However, this is the first formal documentation of the Platessa genus from India.

Platessa arborea C. Radhakrishnan, S. Sherly & B. Karthick sp. nov. (Figs 1–67, Fig. 9 represents the holotype) LM Description (Figs 1–60):—Valve elliptical with narrowly rounded apices. Raphe-sternum valve (RSV): Length: 6.5–9.5 µm, width: 3.5–4.5 µm, ratio length/width: 1.6–2.2 (n = 60). Axial area narrow and hardly discernible, visible only near center of the valve; central area nearly rectangular shape, bordered by 2–3 shorter striae frequently more widely spaced. Striae radiate throughout the valve, 22–24 in 10 µm. Raphe slightly filiform expanded proximal raphe endings. Sternum valve (SV): wide axial area, Length: 6.0–9.0 µm, width: 3.5–4.5 µm. Striae densely arranged 22–24 in 10 µm, parallel at centre, radiate towards apices. SEM Description (Figs 61–67):—Raphe-sternum valve (RSV): Externally, raphe filiform, slight curvature found near ends (Figs 61 & 63). Proximal raphe ends positioned in a broadened shallow groove, distal raphe located in the shallow groove with cone-shaped endings, and both ends slightly bend to the same side (Fig. 61). Striae mostly uniseriate; however found biseriate at 2–3 striae near apices. (Fig. 61). Areolae, apically slit-like throughout the valve, only at the center of the valve it is round-shaped towards axial area (Fig. 61). Internally, proximal raphe ends are strongly hooked, a very remarkable feature which is infrequent in other Platessa species, and its distal ends are curved on opposite sides, terminating in well-developed helictoglossae (Figs 64, 65). Striae lowered between raised virgae. Width of the interstriae is wider than the striae. Striae internally rectangular to round in shape and mostly covered with hymen (Figs 64, 65). An apparent depression is observed on the central nodule (Figs 64, 65). Sternum valve (SV), externally, axial area covered with several irregular shape depressions distributed on the surface of the valve (Fig. 62). Striae uniseriate, however, found biseriate at more than 10 striae near the valve mantle (Fig. 62). Interstriae is raised, and the width of striae is unequal (Fig. 62). Internally, axial area is flat and features are not easily visible (Fig. 66). Biseriate striae found near the mantle with hymenated areolae. Interstriae raised its width slightly more than the striae (Fig. 67). Holotype (designated here):—Slide #58/55, Sample #2878; deposited at the Diatom Collection, Agharkar Research Institute Herbarium (AHMA), Pune, India. Type locality:— INDIA, Sikkim, composite tree moss sample collected on 22 November 2019 on the way to Khecheopalri Lake, West Sikkim district (27.34829 °N, 88.19187 °E; elevation 1794 m a.s.l.) by Radhakrishnan Cheran. Etymology:—Named after the habitat (tree) on which it was found. In Latin, the tree is called an Arbor., Published as part of Sherly, Sheena, Radhakrishnan, Cheran & Karthick, Balasubramanian, 2022, Platessa arborea sp. nov. (Bacillariophyceae): A new tree moss dwelling diatom from the Eastern Himalayas, India, pp. 151-158 in Phytotaxa 552 (2) on pages 152-153, DOI: 10.11646/phytotaxa.552.2.2, http://zenodo.org/record/6690982

Achnanthidium tibeticum Y. Liu & J.P. Kociolek sp. nov. Figures 1���32 Type:����� CHINA. Tibet: Medog County, Yarang Village, Streams, 95��28���22.8 E, 29��29���97.0 N,19 June, 2019. (holotype HANU! Slide no. THTYJZL12, College of Life Science and Technology, Harbin Normal University, Harbin, China. Figs 1 & 2 are of the holotype specimen). Isotype: Material no. YJZL12-12, slide no. YJZL12-12 #. Cleaned material stored in Key laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China. Description:����� LM (Figs 1���14): Raphe valve slightly convex, rapheless valve slightly concave. Valves linear to elliptic, with apices rounded. Length 7.9���3.6 ��m, width 2.9���3.9 ��m (n=25). Axial area narrow and linear. On the raphe valve, striae become coarser in the middle of valve, central area is inconspicuous. On the rapheless valves, central area is absent. On the raphe valves, striae slightly radiate in the center, becoming radiate towards the ends; 9���12 per 10 ��m in center of raphe valve, denser near the ends at 18���20 per 10 ��m. On the rapheless valve, striae nearly parallel in the center and become slightly radiate towards the ends; 12���15 per 10 ��m. SEM: Raphe valve (Figs 15���26): Externally, raphe on the valve face never extends onto the mantle, straight, distal raphe ends?-shaped, curved to the same direction (Figs 15���17, 20), proximal raphe ends slightly expanded, teardrop-shaped. Striae uniseriate, areolae almost round, with varying sizes. One row of slit-like areolae present in the mantle. Internally, raphe straight, distal raphe ends terminate in small helictoglossae, proximal raphe ends curved to the opposite directions. Areolae are occluded by fine hymenate structures. Rapheless valve (Figs 27���32): Externally, axial area narrow and linear; central area absent, areolae almost round. One row of slit-like areolae present on the mantle. Internally, sternum slightly raised on the apices, areolae structure similar to the raphe valve, with finely structured occlusions. Etymology:����� Named for the province of the type locality., Published as part of Ge, Danyang, Zhang, Simeng, Liu, Hongyan, Liu, Yan, Kociolek, Patrick John, Zhu, Huan, Liu, Guoxiang & Fan, Yawen, 2022, One new species of Achnanthidium K��tzing (Bacillariophyta, Achnanthidiaceae) from Tibet, China, pp. 268-280 in Phytotaxa 538 (4) on pages 271-275, DOI: 10.11646/phytotaxa.538.4.1, http://zenodo.org/record/6340368

Tibet is a very important biodiversity hot spot in China and the diatom flora of this region has drawn a lot of attention. Diatom samples were collected from several places across Tibet. During research on the biodiversity of diatoms from Tibet, one Achnanthidium species showed unique features compared with other known taxa. It has linear-lanceolate valves with rounded apices, tear-drop shaped proximal raphe ends and ?-shaped distal raphe ends. The most distinctive character of this species, however, is the shape of areolae; since this species has nearly round external areolar openings on the valve face but more typical slit-like areolae present on the mantle. Here we describe it as new to science as Achnanthidium tibeticum Y. Liu & Kociolek. We compare this new species with other, similar taxa within the genus.

2. Cocconeis capensis (Cholnoky) Witkowski (Figs 9���11) References: Cholnoky 1963, p. 42, figs 6, 7; Witkowski et al. 2000, p. 103, pl. 40, figs 9, 10; Riaux-Gobin et al. 2017, p. 58, figs 20���23. Description: Valves elliptical, 10���17 ��m long, 5���10 ��m wide. SV: sternum linear, and central area not developed. Transapical striae coarse, composed of elongated areolae, 20���22 in 10 ��m, crossed by a hyaline longitudinal line, and radiate towards the apices. Striae as bundle of 1���3 rows of areolae. One row of dense areolae on the margins of valve. A complete frustule is observed (Fig. 12). Remarks: This species was previously reported as Cocconeis clandestina var. capensis Cholnoky from the type locality of the Steanbras River of South Africa (Cholnoky 1963), and from Saldanha Bay of South Africa (Giffen 1976). It occurred in the Azores of Portugal (Stidolph et al. 2012), and in Nagasaki of Japan (Riaux-Gobin et al. 2017). In the Seogwipo coast of Jeju Island, rare in a single sample on seaweeds collected from a small rock pool; it is herein newly described for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on pages 152-154, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Cholnoky, B. J. (1963) Beitrage zur Kenntnis des marinen Litorals von Sudafrika. Botanica Marina 5: 38 - 83. https: // doi. org / 10.1515 / botm. 1963.5.2 - 3.38","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","Riaux-Gobin, C., Compere, P., Straub, F., Ector, L. & Taxbock, L. (2017) Cocconeis voigtii F. Meister (Bacillariophyta) and other species from Meister's and Voigt's Nagasaki (Japan) material. Nova Hedwigia, Beihefte 146: 43 - 62. https: // doi. org / 10.1127 / 1438 - 9134 / 2017 / 043","Giffen, M. H. (1976) A further account of the marine littoral diatoms of the Saldanha Bay Lagoon, Cape Province. South Africa. Botanica Marina 19: 379 - 394. https: // doi. org / 10.1515 / botm. 1976.19.6.379","Stidolph, S. R., Sterrenburg, F. A. S., Smith, K. E. L. & Kraberg, A. (2012) Stuart R. Stidolph Diatom atlas. U. S. geological survey open-file report 2012 - 1163. https: // pubs. usgs. gov / of / 2012 / 1163 /"]}

9. Cocconeis delicata A. Schmidt (Figs 38���41) Basionym: Schmidt et al. 1894b, pl. 196, fig. 24. References: Suzuki et al. 2007, p. 38, figs 15, 16; Riaux-Gobin et al. 2017, p. 52, figs 8, 34���38. Description: Valves elliptical, 21���35 ��m long, 14���25 ��m wide. SV: sternum elliptical, central area not developed. Transapical striae radiate towards the apices, crossed by hyaline and zigzag longitudinal rows, 18���22 in 10 ��m, areolae on a stria transversely elongated, 9���11 in 10 ��m. RV: raphe weakly sigmoid, sternum very narrow. Central area transversely hyaline, occupying the short width of the middle field. Transapical striae radiate towards the apices, 18���22, with 16���23 areolae in 10 ��m of stria. Remarks: This species was originally identified from Yokohama materials by Schmidt et al. (1894b), but very few examples have been reported since. Meister (1935) and Suzuki et al. (2007) reported this species on the coast of Japan, and Riaux-Gobin et al. (2017) described the species in detail, using materials obtained from Nagasaki, Japan. The species was rarely encountered along the Seogwipo coast of Jeju Island. It is herein newly described for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on pages 155-157, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Schmidt, A. (1894 b) Atlas der Diatomaceen-kunde. Leipzig. O. R. Reisland Series V (Heft 49), pls. 193 - 196.","Suzuki, H., Abe, Y., Fujita, D. & Nagumo, T. (2007) Attached diatoms occurring in the aquaculture facility in Kochi Prefectural Deep Seawater Laboratory. Deep Ocean Water Research 8: 27 - 37. [in Japanese] https: // doi. org / 10.11174 / dowas 2000.8.1 _ 27","Riaux-Gobin, C., Compere, P., Straub, F., Ector, L. & Taxbock, L. (2017) Cocconeis voigtii F. Meister (Bacillariophyta) and other species from Meister's and Voigt's Nagasaki (Japan) material. Nova Hedwigia, Beihefte 146: 43 - 62. https: // doi. org / 10.1127 / 1438 - 9134 / 2017 / 043","Meister, F. (1935) Seltene und neue Kieselalgen. I. Berichte der Schweizerischen Botanischen Gesellschaft (Zurich) 4: 87 - 108."]}

11. Cocconeis dirupta var. flexella (Janisch & Rabenhorst) Grunow (Figs 33���37, 90) Basionym: Janisch & Rabenhorst 1863, p. 7, pl. 1, fig. 11. References: Hustedt 1933, p. 355, figs 809d���i; Witkowski et al. 2000. p. 105, pl. 39, figs 6, 7, pl. 51, figs 3���8; De Stefano & Marino 2001, p. 304; Lobban et al. 2012, p. 287, pl. 40, figs 4, 5; Stidolph et al. 2012, pl. 22, figs 25, 30. Description: Valves broadly elliptical to almost circular, 16���31 ��m long and 10���21 ��m wide. SV: sternum moderately broad and sigmoid. Central area not developed, or often a short fascia with missing of a stria in either side of valve. Transapical striae radiate towards apices, crossed by hyaline and longitudinal rows, 20���23 in 10 ��m. RV: striae slightly sigmoid, sternum very narrow. Central area transversely narrow fascia, not reaching to the margins. Transapical striae radiate, 20���21 in 10 ��m. Remarks: The collected variants are distinguished from the nominate variety by the sigmoid sternum of SV (Hustedt 1933). This taxon has been reported from the Mediterranean, some islands of the Pacific and western Indian Oceans (Riaux-Robin et al. 2011, Lobban et al. 2012, Stidolph et al. 2012), Namibia of western Atlantic Ocean (Witkowski et al. 2000), and Mexico (Siqueiros-Beltrones & Romero 2004). This taxon is distributed in warmer coasts and the Mediterranean. Here, it was frequently encountered as epiphytes on seaweeds and the benthic of the sandy bottom of the Seogwipo coast, South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 157, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Janisch, C. & Rabenhorst, L. (1863) Ueber Meeres-Diatomaceen von Honduras. In: Beitrage zur naheren Kenntniss und Verbreitung der Algen. Herausgegeben von Dr. L. Rabenhorst. Leipzig, Verlag von Eduard Kummer 1: 1 - 16, pl. 1 - 4.","Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Ed.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432, figs 781 - 880.","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","De Stefano, M. & Marino, D. (2001) Comparison of Cocconeis pseudonotata sp. nov. with two closely related species, C. notata and C. diruptoides, from Posidonia oceanica leaves. European Journal of Phycology 36: 295 - 306. https: // doi. org / 10.1080 / 09670260110001735458","Lobban, C. S., Schefter, M., Jordan, R. W., Arai, Y., Sasaki, A., Theriot, E. C., Ashworth, M., Ruck, E. C. & Pennesi, C. (2012) Coral-reef diatoms (Bacillariophyta) from Guam: new records and preliminary checklist, with emphasis on epiphytic species from farmer-fish territories. Micronesica 43: 237 - 479.","Stidolph, S. R., Sterrenburg, F. A. S., Smith, K. E. L. & Kraberg, A. (2012) Stuart R. Stidolph Diatom atlas. U. S. geological survey open-file report 2012 - 1163. https: // pubs. usgs. gov / of / 2012 / 1163 /"]}

7. Cocconeis cyclophora var. decora A. Schmidt (Fig. 64) Basionym: Schmidt et al. 1895, pl. 198, figs 1���3. References: Wu et al. 2012, p. 771, pl. 1, fig. e; Riaux-Gobin et al. 2017, p. 58, figs 19, 52���54. Description: Valves elliptical, 33���40 ��m long, 20���22 ��m wide. SV: sternum sigmoid and enlarged between the middle and ends of the valve. A large ocellus in the middle on one side of valve. Transapical striae coarse and radiate towards the apices, 22���26 in 10 ��m, with 17���18 areolae in 10 ��m of stria. Three elliptical hyaline areas lacking areolae on each side of the sternum, the hyaline area in the middle connected to the sternum. No RV observed. Remarks: The variety was reported from the type locality, Yokohama of Japan (Schmidt et al. 1895). It was found in sediments collected from the 1,071m deep bottom surface of the South China Sea (Wu et al. 2012), and in marine benthic materials from Nagasaki of Japan through F. Meister���s collections (Riaux-Gobin et al. 2017). During the survey at Seogwipo coast of Jeju Island, this taxon was encountered twice as epiphytes in small rock pools (St. 2); it is herein newly described for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 155, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Schmidt, A. (1895) Atlas der Diatomaceen-kunde. Leipzig. O. R. Reisland Series V (Heft 50), pls. 197 - 200.","Wu, R., Lan, D., Fang, Q., Chen, C., Lan, B., Sun, L., Gao, Y. & Gao, Y. (2012) First record of genera Rutilaria and Trigonium (Bacillariophyta) and 11 diatom taxa (species and varieties) in South China Sea. Chinese Journal of Oceanology and Limnology 30: 766 - 777. https: // dx. doi. org / 10.1007 / s 00343 - 012 - 1180 - 1","Riaux-Gobin, C., Compere, P., Straub, F., Ector, L. & Taxbock, L. (2017) Cocconeis voigtii F. Meister (Bacillariophyta) and other species from Meister's and Voigt's Nagasaki (Japan) material. Nova Hedwigia, Beihefte 146: 43 - 62. https: // doi. org / 10.1127 / 1438 - 9134 / 2017 / 043"]}

23. Cocconeis stauroneiformis (Rabenhorst) Okuno (Figs 3���5, 103, 104) Basionym: Rabenhorst 1864, p. 101. References: Romero 1996, p. 371, figs 25���54; De Stefano et al. 2000, p. 237, figs 87���92; Witkowski et al. 2000, p. 116, pl. 36, figs 8, 9, pl. 54, figs 1���3; Sar et al. 2003, p. 95, figs 51���57. Description: Valves elliptic-lanceolate to elliptical, 15���20 ��m long, 8���12 ��m wide. SV: sternum moderately linear to lanceolate, and central area not developed. Transapical striae broad, uniseriate, slightly radiate towards the apices, 8���11 in 10 ��m, with 15���16 areolae in 10 ��m of stria. RV: raphe straight, the central ends of raphe close each other, and sternum narrow. Central area transversely expanded into a hyaline fascia, up to the margins. Transapical striae slightly radiate towards the apices, 11 in 10 ��m, with 16���17 areolae in 10 ��m of stria. A hyaline rim in the submarginal area of valve. Remarks: As epiphytic and benthic diatoms, Cocconeis stauroneiformis is distributed widely from the Pacific Ocean to the Antarctica (Romero 1996), and cosmopolitan from marine to brackish waters (Witkowski et al. 2000). It occurred in Gulf of Naples of Italy (De Stefano et al. 2000), and in Patagonian coast of Argentina (Sar et al. 2003). In South Korea, this taxon was reported firstly as the epipsammic from the Nakdong River estuary (Joh 2012), and in this survey, infrequent as the epiphytes on seaweeds along the Seogwipo coast., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 170, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Rabenhorst, L. (1864) Flora Europaea Algarum aquae dulcis et submarinae. Sectio I. Algas diatomaceas complectens, cum figuris generum omnium xylographice impressis. Apud Eduardum Kummerum, Lipsiae. 359 pp.","De Stefano, M., Marino, D. & Mazzella, L. (2000) Marine taxa of Cocconeis on leaves of Posidonia oceanica, including a new species and two new varieties. European Journal of Phycology 35: 225 - 242. https: // doi. org / 10.1080 / 09670260010001735831","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","Sar, E. A., Romero, O. & Sunesen, I. (2003) Cocconeis Ehrenberg and Psammococconeis Garcia (Bacillariophyta) from the Gulf of San Matias, Patagonia, Argentina. Diatom Research 18: 79 - 106. https: // doi. org / 10.1080 / 0269249 X. 2003.9705575","Joh, G. (2012) Freshwater diatoms V: Achnanthaceae. In: Algal flora of Korea. Vol. 3, No. 7. National Institute of Biological Resources, Ministry of Environment, Korea. 134 pp."]}

10. Cocconeis dirupta var. dirupta Gregory (Figs 27���32, 95) Basionym: Gregory 1857, p. 491(19), pl. IX(1), fig. 25. References: Hustedt 1933, p. 354, figs 809a���c; Kobayasi & Nagumo 1985, p. 99, pl. 2. figs 16���27; Witkowski et al. 2000, p. 105, pl. 39, figs 1���5; Riaux-Gobin et al. 2011, p. 26, pl. 3, figs 9���11, pl. 41, figs 1���6; Lobban et al. 2012, p. 286, pl. 40, figs 1���3; Riaux-Gobin et al. 2016, p. 11, figs 4, 35���38 Description: Valves broadly elliptical, 9���23 ��m long, 5���14 ��m wide. SV: sternum narrow to broadly lanceolate, fusiform, sometimes slightly retracted in the middle. Transapical striae radiate, crossed by hyaline and longitudinal rows, 15���22 in 10 ��m, one median stria often shorter on one or both side of the central area. RV: raphe slightly sigmoid. Sternum narrow and straight. Central area not developed or extended as transversely narrrow fascia, not reaching to the margins. Transapical striae radiate, 24���28 in 10 ��m. Remarks: The specimens described herein have valve outlines that are more elliptical rather than round-elliptical to discoid, as described for the lectotype designated by Riaux-Gobin et al. (2016). C. dirupta is distinguished from C. dirupta var. flexella by the straight axial area in the SV. In the literature, Cocconeis dirupta corresponds to two forms: one having large valves with a wide sternum (Kobayasi & Nagumo 1985, Riaux-Gobin et al. 2016) and the other having valves with a strong retraction in the middle of the sternum (Witkowski et al. 2000, Lobban et al. 2012). This species has a wide range in length and width dimensions, and both forms were found in the present study. The identifications were conducted according to the large forms designated by Hustedt (1933), and the small retracted forms by Lobban et al. (2012). The retracted forms collected in local areas have smaller dimensions, 9���17 ��m long and 5���9 ��m wide. In the smaller forms, transapical striae are abruptly denser at apices. This taxon was reportedly common along oceanic coasts (Witkowski et al. 2000), and in tropical coasts (Riaux-Gobin et al. 2011, Lobban et al. 2012). Here, frequent on seaweeds of the Seogwipo coast of South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 157, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Gregory, W. (1857) On new forms of marine Diatomaceae found in the Firth of Clyde and in Loch Fyne, illustrated by numerous figures drawn by K. K. Greville, LL. D., F. R. S. E. Transactions of the Royal Society of Edinburgh 21: 473 - 542, pls. 9 - 14.","Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Ed.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432, figs 781 - 880.","Kobayasi, H. & Nagumo, T. (1985) Observations on the valve structure of marine species of the diatom genus Cocconeis Ehr. Hydrobiologia 127: 97 - 103. https: // doi. org / 10.1007 / BF 00004189","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","Riaux-Gobin, C., Compere, P. & Al-Handal, A. Y. (2011) Species of the Cocconeis peltoides group with a marginal row of unusual processes (Mascarenes and Kerguelen Islands, Indian Ocean). Diatom Research 26: 325 - 338. https: // doi. org / 10.1080 / 0269249 X. 2011.639559","Lobban, C. S., Schefter, M., Jordan, R. W., Arai, Y., Sasaki, A., Theriot, E. C., Ashworth, M., Ruck, E. C. & Pennesi, C. (2012) Coral-reef diatoms (Bacillariophyta) from Guam: new records and preliminary checklist, with emphasis on epiphytic species from farmer-fish territories. Micronesica 43: 237 - 479.","Riaux-Gobin, C., Compere, P., Jordan, R. W., Coste, M. & Yesilyurt, J. C. (2016) Cocconeis molesta Kutz., C. diaphana W. Sm. and C. dirupta W. Greg. (Bacillariophyta): type material, ambiguities and possible synonymies. European Journal of Taxonomy 204: 1 - 18. https: // doi. org / 10.5852 / ejt. 2016.204"]}

18. Cocconeis pseudomarginata Gregory (Figs 69���72) Basionym: Gregory 1857, p. 492, pl. 9, fig. 27. References: Hustedt 1933, p. 359, figs 813a���c; Romero & Navarro 1999, figs 1���6, 13���15, 20���31; Riaux-Gobin et al. 2014a, p. 176, f, 33, 34. Description: Valves broadly elliptical to ovoid, 19���54 ��m long, 10���41 ��m wide. SV: sternum wide lanceolate, the terminal ends of sternum enlarged and pear-shaped, extending to submarginal hyaline line, and a longitudinal row of areolae between sternum and the submarginal hyaline lines. Transapical striae in inner parts of valve radiate towards the apices, 22���29 in 10 ��m, areolae on a stria transapically elongated. RV: raphe straight and linear, sternum very narrow, crescent-shaped hyaline area at the terminal ends of sternum, resulting the ends of raphe distant from the apices. Central area small lanceolate or circular. The valve depressed between the raphe and valve margins. Transapical striae radiate towards the apices, 21���30 in 10 ��m in the inner parts of valve. Remarks: This species is similar to Cocconeis multiperforata De Stefano, Mario & Mazzella and the two may be confused in the image of light microscopy. However, the comprehensive comparison of relevant reports and data of SEM (Romero & Navarro 1999, De Stefano et al. 2000, Mori et al. 2002, Riaux-Gobin et al. 2014a) allowed to identify the following differences: the former has uniseriate striae in the SV, a crescent shape of the hyaline area at the terminal ends of the raphe, and more than 22 of striae in the SV, while these parameters of the latter are biseriate, pear-shaped, and less than 20, respectively. This taxon is widespread along marine coasts worldwide (Hustedt 1933); it has been collected in many places, ranging from Puerto Rico to Scotland (Romero & Navarro 1999). It was reported near Cape Town of South Africa (Giffen 1970), in the southeastern Pacific Ocean and the Caribbean Sea (Romero & Navarro 1999), common in Kattegat of Baltic Sea (Witkowski et al. 2000), and in Japan (Mori et al. 2002). In South Korea, this species was reported as planktons and periphytes off the coast of Jeju Island (Lee et al. 1990, 1991), and in this survey, occurred infrequently as epiphytes in the Seogwipo coast., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on pages 162-166, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Gregory, W. (1857) On new forms of marine Diatomaceae found in the Firth of Clyde and in Loch Fyne, illustrated by numerous figures drawn by K. K. Greville, LL. D., F. R. S. E. Transactions of the Royal Society of Edinburgh 21: 473 - 542, pls. 9 - 14.","Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Ed.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432, figs 781 - 880.","Romero, O. E. & Navarro, J. N. (1999) Two marine species of Cocconeis Ehrenberg (Bacillariophyceae): C. pseudomarginata Gregory and C. caribensis sp. nov. Botanica Marina 42: 581 - 592. https: // doi. org / 10.1515 / BOT. 1999.065","Riaux-Gobin, C., Compere, P. & Ector, L. (2014 a) Some Cocconeis species (Bacillariophyceae) originally described by William Gregory and Robert Kaye Greville from the Firth of Clyde and Loch Fyne (Scotland). Nova Hedwigia 99: 171 - 192. https: // doi. org / 10.1127 / 0029 - 5035 / 2014 / 0190","De Stefano, M., Marino, D. & Mazzella, L. (2000) Marine taxa of Cocconeis on leaves of Posidonia oceanica, including a new species and two new varieties. European Journal of Phycology 35: 225 - 242. https: // doi. org / 10.1080 / 09670260010001735831","Mori, K., Osada, K. & Nagumo, T. (2002) Diatoms from Kamo-ko (Lake Kamo) in Sado Island: vertical distribution of attached diatoms and water quality in summer. Bulletin of the Nippon Dental University, General Education 31: 179 - 191. [in Japanese] https: // doi. org / 10.14983 / 00000561","Giffen, M. H. (1970) New and interesting marine and littoral diatoms from Sea Point, near Cape Town, South Africa. Botanica Marina 13: 81 - 87. https: // doi. org / 10.1515 / botm. 1970.13.2.81","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","Lee, J. B., Go, Y. B. & Choa, J. H. (1990) The structure and dynamics of phytoplankton communities around the coastline of Cheju Island, Korea. Korean Journal of Phycology 5: 159 - 171. [in Korean]","Lee, J. B., Choa, C. H & Kim, I. S. (1991) Distribution and species composition of periphytic diatom around the coast of Cheju Island. Bulletin of Marine Research, Institute of Jeju National University, Jeju, Korea 15: 61 - 72. [in Korean]"]}

14. Cocconeis heteroidea Hantzsch (Figs 77, 78) Basionym: Rabenhorst 1863, p. 21, pl. 6 A, fig. 10. References: Hustedt 1933, p. 256, fig. 811; Suzuki et al. 2001a, p. 131, figs 1���28; Lobban et al. 2012, p. 287, pl. 40, figs 6, 7, pl. 41, figs 1���3. Description: Valves broadly elliptical to almost circular, 36���55 ��m long, 30���47 ��m wide. SV: sternum broadly linear in outline, but distinctly sigmoid. Transapical striae radiate towards the apices, 30, interrupted by a broad longitudinal furrow, and four longitudinal hyaline lines between sternum and the margins, appearing like some longitudinal folds, areolae in a stria transapically elongated. RV: raphe strongly sigmoid, and sternum narrow. Central area small and circular. Valve deeply buried to apical direction between the raphe and the margins, the apical central parts looking prominent in the sigmoid ridge. Transapical striae radiate towards the apices, 23 in 10 ��m. Remarks: This taxon is common in the Mediterranean Sea (Hustedt 1933, Witkowski et al. 2000, Majewska et al. 2013), and was reported for the East Sea of Russia (Orlova et al. 2009) as well as for islands of the Pacific Ocean, Bahamas, and Caribbean Sea (Lobban et al. 2012). It is widely distributed along warmer coasts. In South Korea, it was recorded as plankton off the coast of Jeju Island (Lee et al. 1990), as epiphytes on Zostera in the coast of Geoje Island (Chung & Lee 2008), and in this survey, occurred rarely as epiphytes on seaweeds from small rock pools in Seogwipo coast (St. 2)., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 161, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Rabenhorst, L. (1863) Beitrage zur naheren Kenntnis und Verbreitung der Algen. Part I. Leipzig. 1863. 30 pp., 7 pls.","Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Ed.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432, figs 781 - 880.","Suzuki, H., Nagumo, T. & Tanaka, J. (2001 a) Morphology of the marine epiphytic diatom Cocconeis heteroidea (Bacillariophyceae). Phycological Research 49: 129 - 136. https: // doi. org / 10.1046 / j. 1440 - 1835.2001.00233. x","Lobban, C. S., Schefter, M., Jordan, R. W., Arai, Y., Sasaki, A., Theriot, E. C., Ashworth, M., Ruck, E. C. & Pennesi, C. (2012) Coral-reef diatoms (Bacillariophyta) from Guam: new records and preliminary checklist, with emphasis on epiphytic species from farmer-fish territories. Micronesica 43: 237 - 479.","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","Majewska, R., D'Alelio, D. & De Stefano, M. (2013) Cocconeis Ehrenberg (Bacillariophyta), a genus dominating diatom communities associated with Posidonia oceanica Delile (monocotyledons) in the Mediterranean Sea. Aquatic Botany 112: 48 - 56. https: // doi. org / 10.1016 / j. aquabot. 2013.07.008","Orlova, T. Y., Stonik, I. V. & Shevchenko, O. G. (2009) Flora of planktonic microalgae of Amursky Bay, Sea of Japan. Russian Journal of Marine Biology 35: 60 - 78. https: // doi. org / 10.1134 / S 106307400901009 X","Lee, J. B., Go, Y. B. & Choa, J. H. (1990) The structure and dynamics of phytoplankton communities around the coastline of Cheju Island, Korea. Korean Journal of Phycology 5: 159 - 171. [in Korean]","Chung, M. H. & Lee, K. S. (2008) Species composition of the epiphytic diatoms on the leaf tissues of three Zostera species distributed on the southern coast of Korea. Algae 23: 75 - 81. https: // doi. org / 10.4490 / algae. 2008.23.1.075"]}

4. Cocconeis conspicua A. Schmidt (Figs 87, 105) Basionym: Schmidt et al. 1894b, pl. 196, figs 27���30. Description: Valves broadly elliptical, but slightly oblique along apical axis, 31���38 ��m long, 24���30 ��m wide. SV: sternum broadly elliptical and sigmoid. Longitudinal hyaline area bisecting twice striae between sternum and valve margins, a row of very large puncta on the outer hyaline area, the largest punctum in the area 1.5 ��m in diameter. A longitudinal line crossing striae between the sternum and inner hyaline area. Transapical striae radiate towards the apices, 26���27 in 10 ��m, striae composed of elongated areolae. RV: No RV observed, only trace of sigmoid raphe could be seen. Remarks: This taxon is characterized by a marginal axial hyaline area on each part of the SV and the presence of large round structures in these hyaline areas. There are no descriptions of this taxon except for the illustrations at the times of the naming. From the original valve drawings (Fig. 92) of Schmidt et al. (1894b), valves are 27���38 ��m long and 18���29 ��m wide. At that times, it was found in Kings Mill Islands (now Gilbert Islands) and Samoa in the Pacific Ocean, in Bissex of Barbados in the West Indies, and in Singapore (Schmidt et al. 1894b). However, it is placed on the checklist of marine diatoms in the Caribbean Sea (Navarro and Hern��ndez-Becerril, 1997). Based on the localities found to date, it is a typical tropical taxon. Very rare in a few samples as epiphytes on seaweed in rock pools (St. 2) of Seogwipo coast; it is herein newly described for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 154, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Schmidt, A. (1894 b) Atlas der Diatomaceen-kunde. Leipzig. O. R. Reisland Series V (Heft 49), pls. 193 - 196.","Navarro, J. N. & Hernandez-Becerril, D. U. (1997) Floristicos de Mexico. XV. Check-list of marine diatoms Caribbean Sea. Instituto de Biologia, Universidad Autonoma de Mexico, Mexico. 48 pp."]}

21. Cocconeis scutellum Ehrenberg (Figs 45���48) Basionym: Ehrenberg 1838, p. 194, pl. 14, fig. 8. References: Poulin et al. 1984, p. 56, figs 43���48; Mizuno 1987, p. 592, figs 1���5, 6A���F; De Stefano et al. 2008, p. 508, figs 19���35. Description: Valves elliptic-lanceolate to broadly elliptical, 13���31 ��m long, 12���24 ��m wide. SV: sternum narrow and linear, and central area not developed Transapical striae coarsely punctate, radiate towards the apices, 9���10 in 10 ��m, uniseriate entirely, but bi- and tri-seriate near the mantle, areolae in striae coarsely circular, 9���12 in 10 ��m of stria. RV: A narrow hyaline band in the submarginal area along the valve margin. Striae radiate, 10���13 in 10 ��m, uniseriate, becoming biseriate on the mantle, areolae circular, 16���19 in 10 ��m. Valvocopulae closed, having short fimbriae. Remarks: Cocconeis scutellum is the most commonly reported in taxonomical and ecological research among the genus Cocconeis, but its morphological features have been neglected for a long time in the past. However, with the increase of SEM morphology, C. scutellum was recognized as a complex composed of many heterogeneous taxa rather than a single one (De Stephano et al. 2008). In the meantime, a lot of new taxa have been recently described as new species, and many specimens that have been reported as C. scutellum have been separated as new species (Riaux-Gobin et al. 2013). Therefore, the morphological boundary of the C. scutellum var. scutellum became very important, and it is not easy to identify the nominate variety. The important feature of circumscribing C. scutellum from neighboring species is the poroid areolae on striae of SV, becoming biseriate or triseriate towards the mantle (Mizuno 1987, De Stefano et al. 2008). Loculiferous bands in the margins of the RV, which is fimbriate valvocopulae, is visible. Many frustules of the C. scutellum were also found in the Seogwipo coast, and the morphology of valves was very diverse and there were too many complex morphology and similarities, making it difficult to identify them. Although many images of light and electron microscopy were obtained, accurate identification was difficult. Only two species of C. scutellum and C. speciosa were extracted, and the rest were all set aside for later work. This taxon is widespread and cosmopolitan along the coasts of marine and brackish waters, and has even been found in Antarctic regions (Witkowski et al. 2000, De Stefano et al. 2008). In South Korea, it was reported frequently as planktons and periphytic off the coast (Lee 1995), as epiphytes on Zostera in Geoje Island (Chung & Lee 2008), and as the epipsammic on the sand flat of the Nakdong River estuary (Joh 2012). In this survey, common as epiphytes on seaweeds along the Seogwipo coast, particularly abundant in the lagoon (St. 3)., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on pages 166-167, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Ehrenberg, C. G. (1838) Die Infusionsthierchen als vollkommene Organismen. Ein Blick in das tiefere organische Leben de Natur. Verlag von Leopold Voss, Leipzig. pp. 1 - xvii, 1 - 548, pls. 1 - 64.","Poulin, M., Berard-Therriault, L. & Cardinal, A. (1984) Les diatomees benthiques de substrats durs des eaux marines et saumatres du Quebec. 1. Cocconeioideae (Achnanthales, Achnanthaceae). Le Naturaliste canadien (Rev. Ecol. Syst.) 111: 45 - 61.","Mizuno, M. (1987) Morphological variation of the attached diatom Cocconeis scutellum var. scutellum (Bacillariophyceae). Journal of Phycology 23: 591 - 597. https: // doi. org / 10.1111 / j. 1529 - 8817.1987. tb 04211. x","De Stefano, M., Romero, O. E. & Totti, C. (2008) A comparative study of Cocconeis scutellum Ehrenberg and its varieties (Bacillariophyta). Botanica Marina 51: 506 - 536. https: // doi. org / 10.1515 / BOT. 2008.058","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","Chung, M. H. & Lee, K. S. (2008) Species composition of the epiphytic diatoms on the leaf tissues of three Zostera species distributed on the southern coast of Korea. Algae 23: 75 - 81. https: // doi. org / 10.4490 / algae. 2008.23.1.075","Joh, G. (2012) Freshwater diatoms V: Achnanthaceae. In: Algal flora of Korea. Vol. 3, No. 7. National Institute of Biological Resources, Ministry of Environment, Korea. 134 pp."]}

3. Cocconeis clandestina A. Schmidt (Figs 23, 24) Basionym: Schmidt et al. 1894a, pl. 192, figs 28, 29. References: Hustedt 1933, p. 331, fig. 784; Witkowski et al. 2000, p. 103, pl. 41, figs 20���25. Description: Valves elliptical to nearly circular, 18���29 ��m long, 14���18 ��m wide. SV: sternum narrow and linear. Transapical striae biseriate and radiate towards the apices, 5���6 in 10 ��m, with 10���12 areolae in 10 ��m of stria. No RV observed. Remarks: This taxon is widespread along the coast of northern Europe (Hustedt 1933, Witkowski et al. 2000) and common in the Baltic Sea (Witkowski et al. 2000). In the Seogwipo coast, very rare from small rock pools; it is herein newly described for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 154, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Schmidt, A. (1894 a) Atlas der Diatomaceen-kunde. Leipzig. O. R. Reisland Series IV (Heft 48), pls. 189 - 192.","Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Ed.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432, figs 781 - 880.","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp."]}

16. Cocconeis pelta A. Schmidt (Figs 20, 21) Basionym: Schmidt 1874, p. 93, pl. 3, fig. 17. References: Hustedt 1933, p. 361, fig. 815; Witkowski et al. 2000, p. 111, pl. 41, figs 7���10; Sar et al. 2003, p. 91, fig. 33. Description: Valves elliptical, 15���16 ��m long, 11���12 ��m wide. SV: sternum slightly very broadly lanceolate to elliptical, depressed making a distinct marginal rim, irregularly punctate. Central area not developed. Transapical striae developed in the margins, radiate towards the apices, 17���18 in 10 ��m. RV: raphe straight, sternum broadly elliptical like the SV. Transapical striae in the margins radiate towards the apices. Remarks: The local specimens are smaller than the dimensions reported in referred literatures. Though the fine morphology of the three taxa seen with SEM differs, Cocconeis pelta is similar to C. peltoides Hustedt and C. fluminensis H. Peragallo & M. Peragallo in the morphology of SV under LM. Commonly, the three species have longitudinal costae in the median area of the SV, but the first species is distinguished from the second and the third taxon in that there is no striae in the inside of the longitudinal costae (Sar et al. 2003). The first species has a similar stria density with the second, while it is distinguished from the higher density than the third. This species has been reported from the western Baltic Sea (Witkowski et al. 2000), European coasts in the North Atlantic and the Patagonian coasts of Argentina (Sar et al. 2003). In South Korea, this taxon was reported firstly as the epipsammic from the Nakdong River estuary (Joh 2012), and in this survey, very rare in small rock pools (St. 2) and salt marshes (St. 4) of the Seogwipo coast., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on pages 161-162, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Schmidt, A. (1874) Die in den Grundproben der Nordseefahrt vom 21 Juli bis 9 Sept 1872 enthaltenen Diatomaceen. Erste Folge. Jahresbericht der Kommission zur Untersuchung der Deutsch Meer. Kiel. 2: 81 - 95, 3 pls.","Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Ed.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432, figs 781 - 880.","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","Sar, E. A., Romero, O. & Sunesen, I. (2003) Cocconeis Ehrenberg and Psammococconeis Garcia (Bacillariophyta) from the Gulf of San Matias, Patagonia, Argentina. Diatom Research 18: 79 - 106. https: // doi. org / 10.1080 / 0269249 X. 2003.9705575","Joh, G. (2012) Freshwater diatoms V: Achnanthaceae. In: Algal flora of Korea. Vol. 3, No. 7. National Institute of Biological Resources, Ministry of Environment, Korea. 134 pp."]}

5. Cocconeis convexa Giffen (Figs 42���44, 100���102) Basionym: Giffen 1967, p. 257, figs 26���28. References: Witkowski et al. 2000, p. 104, pl. 37, figs 5, 6, pl. 41, figs 1���4; Suzuki 2001, p. 60, figs 1���35; Riaux-Gobin et al. 2011, p. 22, pl. 3, figs 1���5, pl. 32, figs 1���7. Description: Valves broadly elliptical to almost rhombic, 16���25 ��m long, 12���18 ��m wide. SV: sternum narrow and linear, and central area not developed. Transapical striae parallel at middle, strongly radiate towards the apices, and interrupted by many slightly undulate hyaline lines, 37���41 in 10 ��m. RV: raphe straight, the central ends of raphe slightly curved to the opposite directions, the terminal ends of the raphe distant from the apices without areolation and sternum narrow. Central area expanded transversely to less than half the hemivalve, and central nodule between the central raphe ends thickened. Under the LM, only the thickened central nodule highlighted, making the central area more narrow than it really is. Transapical striae parallel in the middle, strongly radiate towards the apices, 26���31 in 10 ��m of stria, often 1���2 striae in the middle of one side of the valve particularly short. Remarks: Cocconeis convexa is pantropical, and described from the Pacific and Indian Oceans (Witkowski et al. 2000), Guam in the western Pacific Ocean (Navarro & Lobban 2009), R��union and Rodrigues in the western Indian Ocean (Riaux-Gobin et al. 2011), and Tahiti and Tuamotu Archipelago of the southern Pacific Ocean (Riaux-Gobin et al. 2015). The species has been reported from the coasts of Japan (Suzuki 2001), Argentina (Sar et al. 2003), Mexico (Siqueiros-Beltrones & Argumedo-Hern��ndez 2015). In South Korea, it was already reported in the coast of Jeju Island (Kim et al. 2017), and in this survey, was found frequently as epiphytes on seaweeds along the Seogwipo coast., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 154, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Giffen, M. H. (1967) Contributions to the diatom flora of South Africa III. Diatoms of the marine littoral regions at Kidd's Beach near east London, Cape Province, South Africa. Nova Hedwigia 13: 245 - 292, pls. 59 - 63.","Witkowski, A., Lange-Bertalot, H. & Metzeltin, D. (2000) Diatom flora of marine coasts I. Iconographia Diatomologica Vol. 7. A. R. G. Ganter Verlag K. G., Ruggell. 925 pp.","Riaux-Gobin, C., Compere, P. & Al-Handal, A. Y. (2011) Species of the Cocconeis peltoides group with a marginal row of unusual processes (Mascarenes and Kerguelen Islands, Indian Ocean). Diatom Research 26: 325 - 338. https: // doi. org / 10.1080 / 0269249 X. 2011.639559","Navarro, J. N. & Lobban, C. S. (2009) Freshwater and marine diatoms from the western Pacific islands of Yap and Guam, with notes on some diatoms in damselfish territories. Diatom Research 24: 123 - 157. https: // doi. org / 10.1080 / 0269249 X. 2009.9705787","Riaux-Gobin, C., Compere, P. & Jordan, R. W. (2015) Cocconeis Ehrenberg assemblage (Bacillariophyceae) from Napuka Atoll (Tuamotu Archipelago, South Pacific) with descriptions of two new taxa. Diatom Research 30: 175 - 196. https: // doi. org / 10.1080 / 0269249 X. 2015.1021839","Sar, E. A., Romero, O. & Sunesen, I. (2003) Cocconeis Ehrenberg and Psammococconeis Garcia (Bacillariophyta) from the Gulf of San Matias, Patagonia, Argentina. Diatom Research 18: 79 - 106. https: // doi. org / 10.1080 / 0269249 X. 2003.9705575","Siqueiros-Beltrones, D. A. & Argumedo-Hernandez, U. (2015) Epiphytic diatoms grazed by adult abalone (Haliotis spp.) in Baja California Sur, Mexico. Revista Mexicana de Biodiversidad 86: 111 - 122. [in Spanish] https: // doi. org / 10.7550 / rmb. 47977","Kim, B. S., Kim, S. Y., Park, J. G. & Witkowski, A. (2017) New records of the diatom species (Bacillariophyta) from the seaweed and tidal flats in Korea. Korean Journal of Environmental Biology 35: 604 - 621. https: // doi. org / 10.11626 / KJEB. 2017.35.4.604"]}

25. Cocconeis voigtii Meister 1937 (Figs 65���68) Basionym: Meister 1937, p. 266, pl. 10, fig. 5. Reference: Riaux-Gobin et al. 2017, p. 46, figs 1, 24���29. Description: Valves elliptical, 32���58 ��m long, 24���45 ��m wide. SV: sternum broadly lanceolate, the terminal ends of the sternum slightly large and formed as a pear-shaped hyaline area, and connected to the submarginal hyaline band. Transapical striae slightly radiate towards the apices, 17���21 in 10 ��m, crossed by 2���3 longitudinal hyaline lines, outer striae between the sternum and submarginal hyaline band crossed by narrow and wavy longitudinal lines. RV: raphe weakly sigmoid, sternum very narrow and connected to crescent-shaped hyaline area in the apices, the ends of raphe distant from the apices. Central area small and rhombic. A longitudinally depressed area between the raphe and valve margins forming clear submaginal rims. Transapical striae distinctly punctate and radiate towards the apices, striae of inner parts 19���25, with 18���20 areolae in 10 ��m of stria. Remarks: The original description of this taxon was emended by Riaux-Gobin et al. (2017), adding the description of its RV. Previously, the species appears to only have been found at the type locality of Nagasaki, Japan. Along the Seogwipo coast of Jeju Island, it was encountered infrequently as epiphyte from a small rock pool (St. 2), and is herein newly reported for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 170, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Meister, F. (1937) Seltene und neue Kieselalgen. II. Berichte der Schweizerischen Botanischen Gesellschaft (Zurich) 47: 258 - 276, 11 pls.","Riaux-Gobin, C., Compere, P., Straub, F., Ector, L. & Taxbock, L. (2017) Cocconeis voigtii F. Meister (Bacillariophyta) and other species from Meister's and Voigt's Nagasaki (Japan) material. Nova Hedwigia, Beihefte 146: 43 - 62. https: // doi. org / 10.1127 / 1438 - 9134 / 2017 / 043"]}

22. Cocconeis shikinensis Suzuki (Figs 49���52, 96���98) Basionym: Suzuki et al. 2001b, p. 138, figs 1���31. Description: Valves elliptical, 19���50 ��m long, 12���36 ��m wide, the valve surface overall convex, but two-thirds of inner parts on valve face slightly concave. SV: sternum narrow and linear. Central area not developed, but very small circular in large specimens. Transapical striae transversely elongated, radiate towards the apices, 13���17 in 10 ��m, crossed by several hyaline and zigzag longitudinal lines, elongated areolae in striae, alveolus, with 8���10 in 10 ��m of stria. In some valves, often areolae arranged sparsely in the submarginal area. At the marginal area of the valve, one short striae arranged every 1���3 transapical striae, so the striae at the margins more dense than the middle. RV: raphe straight. Sternum narrow, but the terminal ends of the sternum expanded with crescent-shaped hyaline area, resulting the raphe ends distant from the apices. Central area small and circular. Transapical striae radiate, 14���21 in 10 ��m, areolae in striae circular-shaped, with 16���20 areolae in 10 ��m of stria. Valve face between raphe and valve margins depressed concentrically. Remarks: This species is similar to Cocconeis schmidtii Heiden in its valve morphology, but differs in having a crescent hyaline area on the terminal ends of the RV, in lacking a round central hyaline area, and in having a lower density of areolae on both valves (Suzuki et al. 2001b). It was reported as important epiphytes on Caulerpa sp. (Chlorophyta) in Japan (Suzuki 2001b). In the present study, it was mainly found in Rhodophyta, such as Plocamium sp. This species has morphological features that may cause confusion with C. placentula Ehrenberg and its allied taxa. The RV is not so, but the SV is similar to that of C. placentula; thus, judging by the SV alone can be misleading. Prior to the naming of this species, the taxon attached to a carapace in Japan was recorded as C. placentula (Takano 1962). The two species, Cocconeis shikinensis and C. placentula, are sometimes found in the marine coasts. In the present study, the valve length of C. shikinensis ranges from 19 ��m to 50 ��m, while that of C. placentula does from 11 ��m to 36 ��m (Lange-Bertalot et al. 2017). Previously, these taxa had been reported strictly from Japanese coasts, including the type locality, Izu Islands of Tokyo (Suzuki et al. 2001b, 2007). This taxon was encountered infrequently as epiphytes on seaweeds of the Seogwipo coast; it is herein newly described for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 167, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Suzuki, H., Nagumo, T. & Tanaka, J. (2001 b) A new marine diatom, Cocconeis shikinensis sp. nov. (Bacillariophyceae) from Japan. Phycological Research 49: 137 - 144. https: // doi. org / 10.1046 / j. 1440 - 1835.2001.00234. x","Takano, H. (1962) Notes on epiphytic diatoms upon sea-weeds from Japan. Journal of the Oceanographic Society of Japan 18: 29 - 33. https: // doi. org / 10.5928 / kaiyou 1942.18.29","Lange-Bertalot, H., Hofmann, G., Werum, M. & Cantonati, M. (2017) Freshwater benthic diatoms of Central Europe: over 800 common species used in ecological assessments. English edition with updated taxonomy and added species (Cantonati, M. et al. eds). Schmitten-Oberreifenberg: Koeltz Scientific Books. 942 pp., 135 pls.","Suzuki, H., Abe, Y., Fujita, D. & Nagumo, T. (2007) Attached diatoms occurring in the aquaculture facility in Kochi Prefectural Deep Seawater Laboratory. Deep Ocean Water Research 8: 27 - 37. [in Japanese] https: // doi. org / 10.11174 / dowas 2000.8.1 _ 27"]}

13. Cocconeis distans Gregory (Figs 12���19) Basionym: Gregory 1855, p. 39, pl. 4, fig. 9 (incorrect); Gregory 1857, p. 490, pl. 9, fig. 23 (correct) (De Stefano et al. 2006). References: Sar et al. 2003, p. 86, figs 16���21, as Cocconeis guttata Hustedt & Aleem; De Stefano et al. 2006, p. 440, figs 1���7, 15���32. Description: Valves elliptical, often rhombic in large forms, 13���31 ��m long, 8���23 ��m wide. SV: sternum linear, central area not developed. Transapical striae radiate towards the apices, 6���9 in 10 ��m, areolae on striae, coarsely round to subquadrangular and included inflated costae around each areola, 5���9 in 10 ��m of stria. A row of areolae distinct around the margins of valve, on the other hand, among some large forms, two or three small areoale regularly arranged at the terminal ends of each stria in the valve margins (Fig. 13). RV: raphe straight, sternum narrow. Central area not developed. A narrow, hyaline area in the margin borders between valve and mantle. Transapical striae radiate towards the apices, 15���20 in 10 ��m, with 12���19 areolae in 10 ��m of stria. Remarks: Cocconeis distans and C. guttata are occasionally confused due to their similar morphology of valves, and until recently, taxonomic confusion still exists. A close examination of the literature describing the two species found that, before comparing the two taxa, there were two morphotypes in the C. distans, small form and very large form in terms of dimensions of valves. As a result of referring to the literature describing small forms (Gregory 1855, Sar et al. 2003, De Stephano et a. 2006, Riaux-Gobin et al. 2011) and large forms (Cleve 1895, Peragallo and Peragallo 1897-1908, Hustedt 1933, Hendey 1964, Riaux-Gobin et al. 2014a), these two morphotypes are clearly distinguished in valve length (18���31: 28���60 ��m) and valve width (10���20: 17���40 ��m), density of stria (7���11: 4���5 rows in 10 ��m), and density of areolae on a stria (4���8: 12���14 in 10 ��m of SV). Some morphological differences in length or stria densities may be due to the presence of morphological variations. Genetic analyses will precise if it is the same species or varieties. Meanwhile, Hustedt (1933) described C. granulifera Greville as a synonym for C. distans while describing C. distans, and until recently the two species are still considered as a heterotypic synonym. However, the synonym of C. granulifera seems to correspond to the large C. distans. On the other hand, both large and small form of C. distans are clearly distinguished by the difference in the density of the striae on the valve and areolae on the stria. Local taxonomic identity and dimensions of the species are adopted from three references, Sar et al. (2003), De Stefano et al. (2006), and Riaux-Gobin et al. (2011). This taxon is reported from the Patagonian coast of Argentina (Sar et al. 2003) and is distributed throughout the Mediterranean Sea (De Stefano et al. 2006), and common in coral sediments of R��union and Rodrigues in the western Indian Ocean (Riaux-Gobin et al. 2011). It occurred infrequently as benthic diatoms in sand bottoms and salt marshes along the Seogwipo coast of Jeju Island. Local assemblages of the species can be divided into two categories, short and long, based on 23 ��m in length., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on pages 159-161, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Gregory, W. (1855) On a post-Tertiary lacustrine sand, containing Diatomaceous exuviae from, Glenshira, near Inverary. Quarterly Journal of Microscopical Science, London 3: 30 - 43, pl. IV. https: // doi. org / 10.5962 / bhl. title. 64234","Gregory, W. (1857) On new forms of marine Diatomaceae found in the Firth of Clyde and in Loch Fyne, illustrated by numerous figures drawn by K. K. Greville, LL. D., F. R. S. E. Transactions of the Royal Society of Edinburgh 21: 473 - 542, pls. 9 - 14.","De Stefano, M., Sacchi, U., Totti, C. & Romero, O. E. (2006) Cocconeis distans Gregory and Amphicocconeis debesi (Hustedt) De Stefano comb. nov. (Bacillariophyta), an intricate taxonomical history. Botanica Marina 49: 438 - 449. https: // doi. org / 10.1515 / BOT. 2006.055","Sar, E. A., Romero, O. & Sunesen, I. (2003) Cocconeis Ehrenberg and Psammococconeis Garcia (Bacillariophyta) from the Gulf of San Matias, Patagonia, Argentina. Diatom Research 18: 79 - 106. https: // doi. org / 10.1080 / 0269249 X. 2003.9705575","Riaux-Gobin, C., Compere, P. & Al-Handal, A. Y. (2011) Species of the Cocconeis peltoides group with a marginal row of unusual processes (Mascarenes and Kerguelen Islands, Indian Ocean). Diatom Research 26: 325 - 338. https: // doi. org / 10.1080 / 0269249 X. 2011.639559","Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Ed.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432, figs 781 - 880.","Hendey, N. I. (1964) An introductory account of the smaller algae of British coastal waters. Part V: Bacillariophyceae (Diatoms). Ministry of Agriculture, Fisheries and Food, Fishery Investigations. Her Majesty's Stationery Office, London, 317 pp.","Riaux-Gobin, C., Compere, P. & Ector, L. (2014 a) Some Cocconeis species (Bacillariophyceae) originally described by William Gregory and Robert Kaye Greville from the Firth of Clyde and Loch Fyne (Scotland). Nova Hedwigia 99: 171 - 192. https: // doi. org / 10.1127 / 0029 - 5035 / 2014 / 0190"]}

12. Cocconeis cf. diruptoides Hustedt (Figs 25, 26, 91���94) Basionym: Hustedt 1933, p. 356, fig. 810. References: Simonsen 1987, p. 133, pl. 219, figs 5���10, 13, 14; De Stefano & Marino 2001, p. 303, figs 15���27; Car et al. 2012, p. 445, figs S18���21. Description: Valves oblong-elliptical to elliptical, 9���23 ��m long and 5���13 ��m wide. SV: sternum narrow and slightly sigmoid. Central area forming with lacking one striae, expanding into a short hyaline fascia on the one side of valve. Transapical striae slightly radiate towards apices, 25���37 in 10 ��m, areolae on striae transapically elongated, 18���26 in 10 ��m, forming wavy longitudinal lines, a few striae bifurcated in the margins of valve. RV: raphe slightly sigmoid, sternum very narrow. Central area as transversely narrow and hyaline fascia, not reaching up to the margins. Transapical striae slightly radiate, 28���35 in 10 ��m, with 29���35 areolae in 10 ��m of stria. Narrow hyaline area around the margins of valve. Remarks: The local specimens match the description of De Stefano et al. (2000), based on Hustedt���s type specimen, characterized by the presence of hemifascia on SV and strial dichotomy in the margins. However, since the hemifascia is not found in Hustedt���s illustration and the exact type specimens are controversial on the other hand (Riaux-Gobin et al. 2018), the local specimens are recorded as Cocconeis cf. diruptoides. Specimens collected in the current study were often less than 18 ��m long; some were as short as 9 ��m. The species is similar to Cocconeis dirupta var. flexella in its valve morphology, but the latter is distinguished by a sigmoid raphe and sternum of the valve, a low density of transapical striae (De Stefano & Marino 2001), and sparse strial areolae in the SV. In the present survey, this is one of the most commonly observed Cocconeis. The valves are very variable in size and range from 9 ��m to 23 ��m long. In the assemblage, individuals commonly exhibited weakly sigmoidal raphe of valves, but widely differed in the density of striae for both valves. This taxon is distributed in the Mediterranean (Hustedt 1933), has been collected from the northern Adriatic Sea between Rovinj and Vis (De Stefano & Mario 2001), and is widely distributed at temperate and warm coasts (Car et al. 2012). Along the Seogwipo coast, it was found frequently as epiphytes on seaweeds; it is herein newly described for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 159, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Ed.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432, figs 781 - 880.","Simonsen, R. (1987) Atlas and catalogue of the diatom types of Friedrich Hustedt. Vol. 1. Catalogue, 525 pp. Vol. 2. Atlas, Plates 1 - 395, Vol. 3. Atlas, Plates 396 - 772. [J. Cramer, Berlin]","De Stefano, M. & Marino, D. (2001) Comparison of Cocconeis pseudonotata sp. nov. with two closely related species, C. notata and C. diruptoides, from Posidonia oceanica leaves. European Journal of Phycology 36: 295 - 306. https: // doi. org / 10.1080 / 09670260110001735458","Car, A., Witkowski, A., Dobosz, S., Burfeind, D. D., Meinesz, A., Jasprica, N., Ruppel, M, Kurzydlowski, K. J. & Plocinski, T. (2012) Description of a new marine diatom, Cocconeis caulerpacola sp. nov. (Bacillariophyceae), epiphytic on invasive Caulerpa species. European Journal of Phycology 47: 433 - 448. https: // doi. org / 10.1080 / 09670262.2012.735255","De Stefano, M., Marino, D. & Mazzella, L. (2000) Marine taxa of Cocconeis on leaves of Posidonia oceanica, including a new species and two new varieties. European Journal of Phycology 35: 225 - 242. https: // doi. org / 10.1080 / 09670260010001735831","Riaux-Gobin, C., Witkowski, A., Jordan, R. W., Parravicini, V. & Planes, S. (2018) Cocconeis kurakakea, a new diatom species from Nukutavake (Tuamotu Archipelago, South Pacific): description and comparison with C. diruptoides and C. pseudodiruptoides. Phytotaxa 349: 115 - 129. https: // doi. org / 10.11646 / phytotaxa. 349.2.2"]}

1. Cocconeis cf. callosa Meister (Figs 79���83) Basionym: Meister 1937, p. 266, pl. 8, fig. 11. Reference: Riaux-Gobin et al. 2017, p. 57, figs 9, 44���51. Description: Valves rather circular, 27���54 ��m long, 21���49 ��m wide. SV: sternum narrow and bent in opposite directions at the apices, forming a distinct sigmoid curvature. Central area not developed, but only a few areolae missing in the middle to form a small hyaline space. Transapical striae radiate in the middle and strongly radiate towards the apices, 13���15 in 10 ��m, formed by coarse areolae, with 10���11 areolae in 10 ��m of stria. RV: raphe and sternum strongly sigmoid, with opposite curvatures of the terminal ends, both ends of raphe and sternum distant from the apices. Central area extended transversely in a narrow hyaline area not reaching the margins. Transapical striae, 13���14 in 10 ��m distinctly areolae, with 12���16 in 10 ��m of stria. Remarks: Although there was no type specimen of the species, and the morphology of RV was not even described in the original statement, Riaux-Gobin et al. (2017) searched the Meister���s collections, and erected Cocconeis cf. callosa as a legitimate taxon. This species has only been reported from the type locality, Nagasaki in Japan. In the Seogwipo coast of Jeju Island, very rare as epiphytes from a small rock pool (St. 2), representing a new record for South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 152, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Meister, F. (1937) Seltene und neue Kieselalgen. II. Berichte der Schweizerischen Botanischen Gesellschaft (Zurich) 47: 258 - 276, 11 pls.","Riaux-Gobin, C., Compere, P., Straub, F., Ector, L. & Taxbock, L. (2017) Cocconeis voigtii F. Meister (Bacillariophyta) and other species from Meister's and Voigt's Nagasaki (Japan) material. Nova Hedwigia, Beihefte 146: 43 - 62. https: // doi. org / 10.1127 / 1438 - 9134 / 2017 / 043"]}

19. Cocconeis pseudomarginata var. intermedia Grunow (Figs 73���76, 88, 89) Basionym: Grunow 1867, p. 13, pl. 1, fig. 6. References: Suzuki et al. 2001c, p. 94, figs 1���26; Suzuki et al. 2008, p. 277. Description: Valves elliptical, 26���68 ��m long, 14���51 ��m wide. SV: sternum broadly lanceolate, the ends of sternum enlarged and pear-shaped, connected to the submarginal hyaline area, a longitudinal line bisecting striae between sternum and valve margins. The outer surface of sternum longitudinally depressed. Transapical striae radiate towards the apices, 25���30 in 10 ��m, striae composed of elongated areolae. RV: raphe weakly sigmoid, sternum very narrow, the terminal ends of the sternum expanded with a crescent-shaped hyaline area, resulting the raphe distant from the apices. Longitudinal depression between the raphe and valve margins. Central area small rhombic. Transapical striae radiate towards the apices, 23���28 in 10 ��m in the inner parts of valve. Remarks: This taxon differs from the nominate variety, Cocconeis pseudomarginata, in that the raphe is slightly sigmoid and transapical striae of SV are dense. The distribution area of the species is quite limited, compared with the nominate variety, but prefer warmer marine coasts in view of localities, Cape of Good Hope, Nicobar Islands, Luzon, Manilla, and Tahiti (Fourtanier & Kociolek 2011). More recently, it has frequently been found in Japan (Suzuki et al. 2001c). In the present study, it was frequently encountered as epiphytes on seaweeds along the Seogwipo coast of South Korea., Published as part of Joh, Gyeongje, 2021, Distribution of the genus Cocconeis (Bacillariophyceae) along the Seogwipo coast of Jeju Island, South Korea, pp. 149-179 in Phytotaxa 528 (3) on page 166, DOI: 10.11646/phytotaxa.528.3.1, http://zenodo.org/record/5788071, {"references":["Grunow, A. (1867) Reise seiner Majestat Fregatte Novara um die Erde. Botanischer Theil. Band I. Algen. Wien, aus der Kaiselich- Koniglichen Hof-und Staasdruckerei. pp. 104, pls I, Ia, II - XI.","Suzuki, H., Tanaka, J. & Nagumo, T. (2001 c) Morphology of the marine diatom Cocconeis pseudomarginata Gregory var. intermedia Grunow. Diatom Research 16: 93 - 102. https: // doi. org / 10.1080 / 0269249 X. 2001.9705511","Suzuki, H., Nagumo, T. & Tanaka, J. (2008) Morphology and taxonomy of Cocconeis subtilissima Meister (Bacillariophyceae) and two closely related taxa from the coastal waters of Japan. The Journal of Japanese Botany 83: 269 - 279.","Fourtanier, E. & Kociolek, J. P. (2011) Catalogue of diatom names, California Academy of Sciences, on-line version. Available from: [https: // research. calacademy. org / research / diatoms / names / index. asp]"]}

24. Cocconeis suzukii Riaux-Gobin, Compère, Coste, Straub & Taxböck (Figs 57–61, 99) Basionym: Riaux-Gobin et al. 2014b, p. 213, figs 24–28. Description: Valves elliptical, 13–20 μm long, 9–11 μm wide. SV: sternum large, elliptical and slightly sigmoid, not constricted in the middle. Transapical striae delicate and radiate towards the apices, 29–32 in 10 μm, but interrupted by a hyaline longitudinal line, one stria shorter in the middle of one side of valve. RV: both raphe and sternum sigmoid, sternum very narrow, the central ends of raphe close each other, but the terminal ends of raphe relatively far from the apices. Central area not developed. Transapical striae radiate towards the apices, 24–28 in 10 μm. Remarks: This species was designated from F. Meister’s slide specimens, collected from Nagasaki of Japan (Riaux-Gobin et al. 2014b). It does not appear to have been reported anywhere other than Nagasaki. Along Seogwipo coast, the species was encountered less frequently as epiphyte from small rock pools (St. 2); it is herein newly described for South Korea.