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Gomphosphenia minima C. Delgado, S. Blanco, L. González-Paz & S.F.P. Almeida sp. nov. (Figs 2–7 LM, Figs 20–26 SEM) Description:— Frustules in girdle view wedge-shaped (Fig. 24). Valves slightly heteropolar, narrowly clavate to linear-lanceolate with narrowly rounded and not protracted headpole and footpole (Figs 2–7, 20, 23, 25, 26). Largest width near the mid-valve. Valve dimensions (n = 12): length 5.0–8.0 µm, width 2.2–3.0 µm. Axial area rather wide, lanceolate, widening slightly towards the central area (Figs 20, 23, 25, 26). Raphe is straight with slightly expanded drop-like proximal endings (Figs 21–23). Internally, proximal raphe endings are short, unilaterally deflected as small hooks (Figs 20, 22). Distal external raphe endings are very short, straight, slightly expanded into drop-like pores and not extended into the valve mantle (Figs 23, 25, 26). At LM view, striae are difficult to resolve due to the small valve size (Figs 2–7). Transapical uniseriate striae weakly radiate, becoming almost parallel mid-valve, 18–25 striae in 10 μm. Each stria is composed of a single transversely elongated areola both externally and internally (Figs 20–23, 25, 26). A row of individual pores (elongated in the pervalvar direction) is located on the valve mantle in girdle view (Fig. 24). Type:— PORTUGAL. Municipality of Coimbra, district of Coimbra, Centro region, Coimbra subregion: Candal stream, 40°4´44”N, 8°12´10”W, 10th February 2012 (holotype BM 81051! Natural History Museum, London, UK = Fig. 5; isotype: GDA 69158 University of Granada Herbarium, Granada, Spain). Etymology:— The specific epithet minima (from the Latin minimum: very little, very least) refers to the size of this taxon. Distribution and ecology:— Gomphosphenia minima was found in a few of the studied samples. From the 48 samples in the Candal stream, it only occurred in two samples from the same sampling point collected in February 2012 with an average abundance of 0.7 %. It was present in oligotrophic waters (370–910 μg∙L- 1 of nitrate), with neutral pH values (7.7), low electric conductivity (26.3–26.8 μS∙ cm-1) and low water temperature (3.8–8.1 ºC). Associated species: —The diatom assemblage of the type locality (Coimbra) was composed of different species such as Planothidium lanceolatum (Brébisson ex Kützing) Lange-Bertalot (1999: 287) (27.1 %; Figs 7–14), Eunotia minor (Kützing) Grunow (in Van Heurck 1881, figs 20–21) (17.3 %; Figs 19–22, 45), Planothidium frequentissimum (Lange-Bertalot) (in Lange-Bertalot 1999: 282) (16.8 %; Figs 15–18, 41, 42) and Sellaphora nigri (De Notaris) Wetzel & Ector (2015: 221, Figs 319–393) (11.4 %; Figs 23–33, 43, 44)., Published as part of González-Paz, Lorena, Almeida, Salomé F. P., Blanco, Saúl & Delgado, Cristina, 2022, A new species of an unexplored diatom genus: Gomphosphenia minima sp. nov. (Cymbellales, Rhoicospheniaceae), pp. 135-148 in Phytotaxa 554 (2) on page 138, DOI: 10.11646/phytotaxa.554.2.3, http://zenodo.org/record/6820923, {"references":["Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus Achnanthes Bory (sensu lato). Iconographia Diatomologica 6: 276 - 289.","Wetzel, C. E., Ector, L., Van de Vijver, B., Compere, P. & Mann, D. G. (2015) Morphology, typification and critical analysis of some ecologically important small naviculoid species (Bacillariophyta). Fottea 15 (2): 203 - 234. https: // doi. org / 10.5507 / fot. 2015.020"]}

International audience; A new Gomphosphenia species (Bacillariophyceae) was found during a diatom survey in the “Réserve Naturelle Nationale de la Vallée de Chaudefour” (RNN VC), in the Massif Central (France). Gomphosphenia vallei sp. nov. is described from stone surfaces in Pérouse Stream, Auvergne, France. A detailed description of morphology of G. vallei is presented, based on light and scanning electron microscopy. This new small-sized species is characterized by linear-clavate to elliptical valves. Striae are uniseriate and composed of single slit-like areolae, an axial area linear and narrow and a low number of striae. Gomphosphenia vallei seems to inhabit headwater stream.

Gomphosphenia vallei Beauger, C.E.Wetzel, Allain & Ector sp. nov. (Figs 2 –45) Light microscopy observations (Figs 2–25): Valves linear-clavate in larger specimens to clavate in smaller ones and elliptical in the smallest individuals. Headpoles rounded, footpoles narrowly rounded. Valve dimensions (n = 30): length 4.2–13.1 µm, width 1.5–2.5 µm. Raphe straight, filiform. Striae visible in LM, almost parallel throughout the valve to slightly radiate in the mid-valve, 23–29 in 10 µm. Axial area linear and narrow. Central area from absent to asymmetrical with round and distinct central nodule. In girdle view, frustules almost rectangular to slightly wedgeshaped. Scanning electron microscopy observations (Figs 26–33): Valve face flat. Externally, striae composed of single slit-like areolae, becoming very short slit near the poles (Figs 26–30). Striae slightly radiate in central part of valve, becoming convergent towards both head and footpoles. Raphe straight, filiform, with slightly dilated distal and proximal raphe endings (Figs 26–30). Distal raphe fissures terminating on the valve face, not extending onto the valve mantle (Fig. 28). Internally, proximal raphe endings bent in the same direction (Fig. 31). Internal terminal raphe fissures ending in helictoglossae (Fig. 31). Single row of slit-like areolae located on the valve mantle (Figs 26, 28, 30, 32), sometimes rounded in shape near the mid-valve and towards the footpole (Figs 27, 33). Central area with a unilateral fascia, with a short areola on one side and absence of areola on the other side (Figs 26–29). Central nodule slightly raised (Fig. 31). Apical pore fields absent (Fig. 28). In girdle view, frustules with cingulum composed of open bands, each bearing one row of small round pores (Figs 28, 30, 32–33). Type locality: — FRANCE. Chambon-sur-Lac, “Réserve Naturelle Nationale de la Vallée de Chaudefour”: Pérouse Stream, sample PER _200821, 1,184 m a.s.l., E688534.487, N6493049.143 (Lambert 93), collection date 20 August 2021 (assigned here, holotype: CLF!, slide no. CLF310234; isotype: BR! slide no. BR-4707. The holotype is represented by Fig. 12). Etymology: — This species is named for Eric Vallé, curator of the National Nature Reserve and passionate about botany. Ecology and associated diatom taxa: — The Pérouse Stream, situated in the glacial cirque of Chaudefour Valley, is characterized by a low conductivity (35 μS cm-1), a low temperature (11.9 °C) and is well oxygenated (92.9% of dissolved oxygen) (Table 1). The pH is 7.09. As underlined the conductivity, the concentrations of the measured ions are low with a maximum for the sodium concentration (2.53 mg L- 1). The type population of G. vallei was found in Pérouse Stream associated with other taxa. In August 2021, the two co-dominant taxa were Planothidium lanceolatum (Brébisson ex Kützing 1846: 247) Lange-Bertalot (1999: 287) (36%) and Rhoicosphenia abbreviata (C. Agardh 1831: 34) Lange-Bertalot (1980: 586) (30%). The other species well represented (Achnanthidium subatomus (Hustedt 1939: 554) Lange-Bertalot (1999: 273) (7.1%), Gomphonema sp. cf. minutum C. Agardh (1831: 34) (6.4%), Navicula reichardtiana Lange-Bertalot in Lange-Bertalot & Krammer (1989: 163) (2.3%), Odontidium mesodon (Ehrenberg 1839: 57) Kützing (1849: 12) (2.3%), Gomphosphenia vallei (2.3%), Reimeria sinuata (W. Gregory 1856: 4) Kociolek & Stoermer (1987: 457) (1.9%), Planothidium curtistriatum C.E.Wetzel, Van de Vijver & Ector in Wetzel et al. (2019: 61) (1.9%), Cocconeis rouxii Héribaud & Brun in Héribaud (1893: 45) (1.9%) and Encyonema minutum (Hilse in Rabenhorst 1862: No. 1261) D.G.Mann in Round et al. (1990: 667) (1.1%). At last, Chamaepinnularia obsoleta (Hustedt 1942a: 69) C.E.Wetzel & Ector in Wetzel et al. (2013: 158), Cyclotella antiqua W. Smith (1853: 28), Geissleria acceptata (Hustedt 1950: 398) Lange-Bertalot & Metzeltin (1996: 64), Gomphonema clavatum Ehrenberg (1832: 88), Gomphonema exilissimum (Grunow in Van Heurck 1880: pl. 25, fig. 12) Lange-Bertalot & E.Reichardt in Lange-Bertalot & Metzeltin (1996: 70), Humidophila perpusilla (Grunow 1860: 552) R.L.Lowe, Kociolek, J.R.Johansen, Van de Vijver, Lange-Bertalot & Kopalová (2014: 358), Mayamaea permitis (Hustedt 1945: 919) Bruder & Medlin (2008: 327), Meridion constrictum Ralfs (1843: 458), Nitzschia hantzschiana Rabenhorst (1860: 40), Nitzschia soratensis E.Morales & M.L.Vis (2007: 128), Nupela lapidosa (Krasske 1929: 350) Lange-Bertalot (1999: 274), Pantocsekiella ocellata (Pantocsek 1901: 134) K.T.Kiss & Ács in Ács et al. (2016: 62), Pinnularia sinistra Krammer (1992: 105), Psammothidium helveticum (Hustedt 1933: 385) Bukhtiyarova & Round (1996: 8), Psammothidium subatomoides (Hustedt in Schmidt 1936: pl. 404) Bukhtiyarova & Round (1996: 13) and Sellaphora atomoides (Grunow in Van Heurck 1880: 107) C.E.Wetzel & Van de Vijver in Wetzel et al. (2015: 219) represented less than 1% of the whole community., Published as part of Beauger, Aude, Allain, Elisabeth, Voldoire, Olivier, Blavignac, Christelle, Rossi, Sofia, Wetzel, Carlos E. & Ector, Luc, 2022, Gomphosphenia vallei (Bacillariophyta), a new diatom species from a stream in the " Réserve Naturelle Nationale de la Vallée de Chaudefour ", Massif Central (France), pp. 167-179 in Phytotaxa 542 (2) on pages 170-173, DOI: 10.11646/phytotaxa.542.2.4, http://zenodo.org/record/6415941, {"references":["Kociolek, J. P., Laslandes, B., Bennett, D., Thomas, E., Brady, M. & Graeff, C. (2014) Diatoms of the United States, 1 Taxonomy, ultrastructure and descriptions of new species and other rarely reported taxa from lake sediments in the western U. S. A. Bibliotheca Diatomologica 61: 1 - 188.","Thomas, E. W., Kociolek, J. P., Lowe, R. L. & Johansen, J. R. (2009) Taxonomy, ultrastructure and distribution of gomphonemoid diatoms (Bacillariophyceae) from Great Smoky Mountains National Park (U. S. A.). Diatom taxonomy, ultrastructure and ecology: modern methods and timeless questions. A tribute to Eugene F. Stoermer. Nova Hedwigia, Beiheft 135: 201 - 237.","Kutzing, F. T. (1846) Kurze Mittheilung uber einige kieselschalige Diatomeen. Botanischen Zeitung 4: 247 - 248.","Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus Achnanthes Bory (sensu lato). Iconographia Diatomologica 6: 276 - 289.","Agardh, C. A. (1831) Conspectus criticus diatomacearum. Part 3. Lundae Literis Berlingianus: 33 - 48.","Lange-Bertalot, H. (1980) Ein Beitrag zur Revision der Gattungen Rhoicosphenia Grun., Gomphonema C. Ag., Gomphoneis Cl. Botaniska Notiser 133: 585 - 594.","Hustedt, F. (1939) Die Diatomeenflora des Kustengebietes der Nordsee vom Dollart bis zur Elbemundung. I. Die Diatomeenflora in den Sedimenten der unteren Ems sowie auf den Watten in der Leybucht, des Memmert und bei der Insel Juist. Adhandlungen des Naturwissenschaftlichen Verein zu Bremen 31 (2 / 3): 571 - 677, 123 figs.","Ehrenberg, C. G. (1839) Uber das im Jahre 1686 in Curland vom Himmel gefallene Meteorpapier und uber dessen Zusammensetzung aus Conferven und Infusorien. Abhandlungen der Koniglichen Akademie der Wissenschaften zu Berlin 1838: 45 - 58.","Kutzing, F. T. (1849) Species Algarum. F. A. Brockhaus, Lipsiae [Leipzig], 922 pp. http: // dx. doi. org / 10.5962 / bhl. title. 60464","Gregory, W. (1856) Notice of some new species of British freshwater Diatomaceae. Quarterly Journal of Microscopical Science, New Series 4: 1 - 14.","Kociolek, J. P. & Stoermer, E. F. (1987) Ultrastructure of Cymbella sinuata and its allies (Bacillariophyceae), and their transfer to Reimeria, gen. nov. Systematic Botany 12 (4): 451 - 459. https: // doi. org / 10.2307 / 2418882","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","Heribaud, J. (1893) Les Diatomees d'Auvergne. Pensionnat des Freres des Ecoles Chretiennes, Clermont-Ferrand & Librairie des Sciences Naturelles, Paris, 255 pp., 6 pls.","Rabenhorst, L. (1862) Die Algen Europa's, Fortsetzung der Algen Sachsens, Resp. Mittel-Europa's, Dresden. Decas, 25 - 26, nos 641 - 660.","Round, F. E., Crawford, R. M. & Mann, D. G. (1990) The diatoms: biology & morphology of the genera. Cambridge University Press, Cambridge, 747 pp.","Hustedt, F. (1942 a) Susswasser-Diatomeen des indomalayischen Archipels und der Hawaii-Inslen. Internationale Revue der gesamten Hydrobiologie und Hydrographie 42 (1 / 3): 1 - 252.","Wetzel, C. E., Martinez-Carreras, N., Hlubikova, D., Hoffmann, L., Pfister, L. & Ector, L. (2013) New combinations and type analysis of Chamaepinnularia species (Bacillariophyceae) from aerial habitats. Cryptogamie, Algologie 34 (2): 149 - 168. http: // dx. doi. org / 10.7872 / crya. v 34. iss 2.2013.149","Smith, W. (1853) A synopsis of the British Diatomaceae; with remarks on their structure, function and distribution; and instructions for collecting and preserving specimens. The plates by Tuffen West. In two volumes. London: John van Voorst, Paternoster Row, 33 pp.","Hustedt, F. (1950) Die Diatomeenflora norddeutscher Seen mit besonderer Berucksichtigung des holsteinischen Seengebiets. V - VII. Seen in Mecklenburg, Lauenburg und Nordostdeutschland. Archiv fur Hydrobiologie 43: 329 - 458.","Lange-Bertalot, H. & Metzeltin, D. (1996) Oligotrophie-Indikatoren. 800 Taxa reprasentativ fur drei diverse Seen-Typen. Kalkreich - Oligodystroph - 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.","Ehrenberg, C. G. (1832) Uber die Entwickelung und Lebensdauer der Infusionsthiere; nebst ferneren Beitragen zu einer Vergleichung ihrer organischen Systeme. Abhandlungen der Koniglichen Akademie Wissenschaften zu Berlin, Physikalische Klasse 1831: 1 - 154.","Van Heurck, H. (1880) Synopsis des Diatomees de Belgique Atlas. Ducaju et Cie, Anvers, pl. 1 - 30.","Grunow, A. (1860) Uber neue oder ungenugend gekannte Algen. Erste Folge, Diatomeen, Familie Naviculaceen. Verhandlungen der Kaiserlich-Koniglichen Zoologisch-Botanischen Gesellschaft in Wien 10: 503 - 582, pl. III - VII.","Hustedt, F. (1945) Diatomeen aus Seen und Quellgebieten der Balkan-Halbinsel. Archiv fur Hydrobiologie 40 (4): 867 - 973.","Bruder, K. & Medlin, L. K. (2008) Morphological and molecular investigations of naviculoid diatoms. II. Selected genera and families. Diatom Research 23 (2): 283 - 329. https: // doi. org / 10.1080 / 0269249 X. 2008.9705759","Ralfs, J. (1843) On the British species of Meridion and Gomphonema. Annals and Magazine of Natural History 12: 457 - 467.","Rabenhorst, L. (1860) Erklarung der Tafel VI. Hedwigia 2: 40, 6 / 6.","Krasske, G. (1929) Beitrage zur Kenntnis der Diatomeenflora Sachsens. Botanisches Archiv 27 (3 - 4): 347 - 380, 1 pl.","Pantocsek, J. (1901 ' 1902 ') A Balaton kovamoszatai vagy Bacillariai. A Balaton tudomanyos tanulmanyozasanak eredmenyei. Hornyansky Konyvnyomdaja, Budapest, 143 pp., 17 pls.","Acs, E., Ari, E., Duleba, M., Dressler, M., Genkal, S. I., Jako, E., Rimet, F., Ector, L. & Kiss, K. T. (2016) Pantocsekiella, a new centric diatom genus based on morphological and genetic studies. Fottea 16 (1): 56 - 78. https: // doi. org / 10.5507 / fot. 2015.028","Krammer, K. (1992) Pinnularia. Eine Monographie der europaischen Taxa. Bibliotheca Diatomologica 26: 1 - 353.","Hustedt, F. (1933) Die Kieselalgen Deutschlands, Osterreichs und der Schweiz unter Berucksichtigung der ubrigen Lander Europas sowie der angrenzenden Meeresgebiete. In: Rabenhorst, L. (Eds.) Kryptogamen Flora von Deutschland, Osterreich und der Schweiz. Akademische Verlagsgesellschaft m. b. h. Leipzig 7 (Teil 2, Lief. 3): 321 - 432.","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): 1 - 30. https: // doi. org / 10.1080 / 0269249 X. 1996.9705361","Schmidt, A. (1936) Atlas der Diatomaceen-kunde. Leipzig. O. R. Reisland, Series VIII (Heft 101 - 102): pls. 401 - 408.","Wetzel, C. E., Ector, L., Van de Vijver, B., Compere, P. & Mann, D. G. (2015) Morphology, typification and critical analysis of some ecologically important small naviculoid species (Bacillariophyta). Fottea 15 (2): 203 - 234. https: // doi. org / 10.5507 / fot. 2015.020"]}

Gomphosphenia patrickiana Cantonati, Lange-Bert., Kociolek & A.A.Saber, sp. nov. (Figs 4-6) TYPE MATERIAL. — Unites States. Puerto Rico, Cupeyes Stream, National Forest, south-western part of the Island of Puerto Rico, lithology: serpentinites (metamorphic rocks), (18°06’48.65”N, 66°59’12.30”W, 166 m a.s.l.), 3.II.2016 (holo-, ANSP, slide NEON00303 b, partly shown here in Fig. 4; iso-, BM, slide BM 81900; iso-: TR, slide cLIM004 DIAT 3904; NEON Biorepository, Arizona State University’s Natural History Collection in Tempe, AZ, slide NEON 00303 a; diatom collection of the Botany Department, Faculty of Science, Ain Shams University, Egypt, slide PBA– DIAT 2001). REGISTRATION. — http://phycobank.org/102720 ETYMOLOGY. — The specific epithet “ patrickiana ” is named in honor of the United States phycologist and limnologist specializing in diatoms and hydrobiology, Ruth M. Patrick (1907-2013). She developed innovative ways to assess the quality of freshwater ecosystems, in particular using diatoms, authored>200 scientific papers, and established numerous research facilities, in particular the Phycology Section at the Academy of Natural Sciences of Philadelphia (ANSP, part of Drexel University since 2011). We consider this last achievement notable in the international museological context, as a bright example of a part of the research division (ANSP’s Patrick Center for Environmental Research) of a science museum that obtains most of its funding from tenders, consulting, and ecological assessment projects, many carried out at a nation-wide scale. MORPHOLOGY Light microscopy (Fig. 4 M-U) Frustules wedge-shaped in girdle view (Fig.4M - U).Valves linearclavate in larger specimens to clavate in smaller ones, slightly broader at the central area in the larger specimens, the headpoles rounded whilst the footpoles are narrowly rounded (Fig. 4 A-L), 8.0-17.5 µm long, 2.5-4.0 µm wide, L/W ratio: 3.4-4.8. Axial area lanceolate to moderately narrower in the smaller specimens, in general narrow at the poles and gradually widening towards the central part. Central area ± rhombic, mostly with 2-4 shortened striae, and in some specimens transversely expanded to the valve margin on one side forming a unilateral fascia (Fig. 4C). The raphe straight, filiform with distinct proximal endings. Striae radiate throughout the valve, becoming almost parallel near the head- and footpole, 23-27 in 10 µm. Scanning electron microscopy (Figs 5; 6) The valve face is flat, without stigma. Striae on the valve exterior composed of single radiate slit-like areolae ‘foramina’, becoming almost round poroids near the poles, particularly the footpole (Fig. 5A, B). Central area in some specimens with a broad unilateral fascia (Fig. 5A), and slightly broader in the larger specimens (Fig. 5B). Raphe straight, filiform with distinctly dilated proximal raphe endings, and distal raphe fissures terminating on the valve face, not extending into the valve mantle, with teardrop-shaped pores (Fig. 5A, B). The valve mantle bears a single row of areolae which are slit-like at the upper valve half and the headpoles but rounded in shape near the mid-valve and towards the footpole (Fig. 6C, D). Internally, septa and pseudosepta at both poles are absent (Fig. 5C; 6F, G). Internal foramina have almost the same size as the external areolae, and are occluded by hymenes (Fig. 5C, D). Central nodule is slightly raised (Fig. 5D). Internal proximal raphe endings are T-shaped (Fig. 5C, D), while the internal terminal raphe fissures terminate in relatively large helictoglossae (Fig. 6A, B). In girdle view, frustules typically wedge-shaped, with cingulum composed of seven open bands, each bearing one row of small round pores. Apical pore fields absent (Fig. 6C, D, E). ECOLOGY AND CO- OCCURRING DIATOM SPECIES So far, G. patrickiana has been observed only as a Neotropical epilithic species in the two rivers Rio Cupeyes and Rio Guilarte, located in southwest Puerto Rico. It was reported in 27 out of the 37 samples investigated from Rio Cupeyes, and in 21 out of the 45 samples from Rio Guilarte. Maximum relative abundance was distinctly higher in Rio Cupeyes (43%) compared to Rio Guilarte (3%). The Rio Cupeyes is, in general, characterized by a water quality much better than that of the agricultureimpacted Rio Guilarte stream, in terms of average TDN and TDP values (Fig. 1). Only epilithon samples were available for this study but they were collected from different habitats and stream reaches (within the same station). Table 1 shows the distribution of the species (using per cent relative abundance) with respect to stream and microhabitat, showing that it was clearly more abundant and frequent in the Rio Cupeyes (Kruskal-Wallis chi-squared “streams” = 14.37, d.f. = 1, p = 0.0001). Similar results were obtained for microhabitats (Kruskal-Wallis chisquared “habitats” = 11.01, d.f. = 2, p = 0.004) and seasons (Kruskal-Wallis chi-squared “seasons” = 10.92, d.f. = 2, p = 0.004). However, a three-way ANOVA showed that the interaction among these three factors is significant (factor = river × season, d.f. = 2, F = 8.20, p = 0.001; factor = season x habitat, d.f. = 4, F = 3.95, p = 0.006). The predominant diatom species (relative abundance> 5%) of the most common genera at the type locality (Rio Cupeyes) during the whole period of study were: Gogorevia constricta (Torka) Kulikovskiy & Kociolek, Achnanthidium jackii Rabenhorst, Adlafia neoniana Cantonati, Denticula occidentalis Østrup, Gomphonema neotropicum N.Abarca & D.Mora, Nitzschia paleacea (Grunow) Grunow, Sellaphora saugerresii (Desmazières) C.E. Wetzel & D.G. Mann, and Ulnaria lanceolata (Kützing) Compère. Predominant species (rel. ab.> 5%) at the Rio Guilarte were: Achnanthidium eutrophilum (Lange-Bert.) Lange- Bert., Cocconeis placentula var. euglypta (Ehrenberg) Grunow, C. placentula var. lineata (Ehrenberg) Van Heurck, Craticula subminuscula (Manguin) C.E. Wetzel & Ector, and Cymbella turgidula Grunow, Gomphonema kobayasii Kociolek & J.C. Kingston, Halamphora veneta (Kützing) Levkov, Nitzschia cf. palea (Kützing) W.Smith, Sellaphora nigri (De Notaris) Wetzel & Ector, Ulnaria monodii (Guermeur) Cantonati & Lange- Bert., and U. ramesii (Héribaud) T. Ohtsuka., Published as part of Saber, Abdullah A., Angeli, Nicola, Lange-Bertalot, Horst, Kociolek, John P., Spitale, Daniel, Charles, Donald F. & Cantonati, Marco, 2021, Rise of subgen. Rhoicosphenula Lange-Bert. to the genus level, and description of a new Gomphosphenia s. s. species from Puerto Rico, pp. 217-229 in Cryptogamie, Algologie 20 (13) on pages 222-224, DOI: 10.5252/cryptogamie-algologie2021v42a13, http://zenodo.org/record/7819267

Background and aims – Hustedt (1942) originally described Gomphosphenia tackei from Germany under the name Gomphonema tackei. Because of the small cell size and the lack of scanning electron microscopy (SEM) images from the type material, it is often confused with other species from this genus, especially with G. stoermeri. The aim of this paper was to present detailed morphological characteristics of G. tackei based on the analysis of the type material and of several epizoic populations from Central Europe. Material and methods – The material in this study was collected from the shells of the freshwater snails Lymnaea stagnalis, Planorbarius corneus, and Planorbis planorbis. Additionally, for an unambiguous species identification, the type material for Gomphosphenia tackei was analyzed using light and scanning electron microscopes.Key results – The presence of Gomphosphenia tackei was confirmed in the studied material. The largest population (up to 19%) was recorded on the shell surfaces of living snails, whereas on empty shells, the diatom did not seem to be present or only in very low numbers. Valves are typically clavate with rounded apices. Valves are frequently observed in girdle view, often joint together in pairs. The valves in the studied populations had a valve length of 7–29 µm, a valve width of 3–4 µm, and a stria density of 25–29 striae in 10 µm. In the type population, valve length ranged from 7.5 to 27 µm with a valve width of 3.0–4.0 µm and a stria density of 23–29 striae per 10 µm. Striae were composed of 2–4 elongated to rounded areolae per stria. At the apices, the striae were composed of one single areola. The cells were attached to the substratum by their footpole.Conclusion – Published illustrations of Gomphosphenia tackei do not always correctly represent this species. Individual cells are attached to the substratum by secreted mucilage, probably via their areolae or girdle band pores located on the footpole.

Crveno jezero (Red Lake) is one of the largest karstic sinkhole lakes in the Europe. Diatom flora of this lake was unknown due to difficulties in collecting samples. Recently, samples were collected by speleodivers in the frame of systematical natural sciences research, during the cave diving expedition “Crveno jezero 2017” and observations revealed the existence of a new species, Gomphosphenia plenkoviciae Gligora Udovič & Žutinić sp. nov. The species is described herein as new to science based on light and scanning electron microscopy. Gomphosphenia plenkoviciae is characterized by having narrowly clavate to linear valves, which are slightly heteropolar in larger specimens to clavate in smaller specimens, thus differing from the closest taxon by the valve outline and shape of the central area. Smaller valves of G. plenkoviciae differ from other small-sized Gomphosphenia species by valve outline, striae morphology and the shape of axial and central areas.

Gomphosphenia tenuis Levkov & D.M.Williams, sp. nov. (Figs 131–139, 161–171) Valvae distinctius lineari-clavatae verticibus distincte obtusius rotundatis quam basipoli. Longitudo valvae 22–42 µm, latitudo valvae 3.5–6.2 µm. Raphe filiformis poris centralibus distinctis. Area axialis variabilis, modice angusta quoad specimina minora sed lata quoad specimina maiora. Area centralis lata unilateraliter fasciam formans. Striae transapicales breves submarginales, radiantes to subparallelae 14–16 in 10 µm. Type:— MACEDONIA. Lake Ohrid, Bay of St. Naum, rock scrape, small spring, collection date: 17 March 2007 (accession No. MKNDC 001124). Slide BM 101475 (holotype). Slide MKNDC 001124 (isotype). Valves distinctly club-shaped, narrowly linear, head poles more obtusely rounded than foot poles. Valve length 22–42 µm, valve width 3.5–6.2 µm. Raphe filiform with distinct central pores. Axial area variable, moderately narrow in smaller specimens, wide in larger specimens. Central area a broad unilateral fascia. Striae short, submarginal, radial to subparallel, 14–16 in 10 µm. (LM). Valve face flat, transition of valve face to mantle forms a gentle right angle (Fig. 161). Valve mantle fairly high, possessing single row of round to slit-like pores (Fig. 161). Raphe branches straight, not passing onto valve mantle (Figs 162, 163). Raphe proximally and distally expanded, terminating with tear-drop-shaped pores (Figs 165, 166). Central pores slightly unilaterally deflected (Fig. 164). Striae each composed of a single areola of variable shape; usually one central stria absent. Areolae near central area and apices have round foramina (Figs 164, 165); remaining areolae are narrow slits positioned near valve margin. Apical pore field absent on both poles. Internally, pseudoseptum absent at both poles (Figs 167, 169). Raphe branches straight, proximally terminate with anchor-shaped fissures (Figs 168, 170), distally with small helictoglossae (Fig. 171). Central nodule is elevated slightly from rest of valve (Fig. 170). Internal openings of areolae much longer than external, occluded by hymenes (SEM). Observations:— Gomphosphenia tenuis belongs to subgenus Gomphosphenia (Lange-Bertalot 1995) and is characterized by T-shaped internal central raphe endings and the absence of both a septum and pseudoseptum; the opposite is found in the subgenus Rhoicosphenula. Gomphosphenia tenuis closely resembles G. lingulatiformis (Lange-Bertalot & Reichardt) Lange-Bertalot (1993: figs 83: 1–11; Lange- Bertalot 1995: figs 4: 1–4). Differences between the two concern the valve shape. The valves of G. lingulatiformis widen at the middle (the margin is undulated) and the valve apices are distinctly cuneate. Gomphosphenia tenuis can easily be differentiated from G. grovei var. lingulata (Hustedt) Lange-Bertalot (Hustedt 1927b: fig. 5:5, Simonsen 1987: figs 162: 1–7) by the valve shape and the shape of central and axial area. Gomphosphenia tackei (Hustedt) Lange-Bertalot (Hustedt 1942: figs 16–18, Simonsen 1987: figs 459: 7–15) has a similar valve outline to G. tenuis but can be easily differentiated by the narrower valves (B= 2.5– 3.5 µm), finely punctate striae and very narrow central and axial areas. Gomphonema tackei var. brevistriatum Camburn (in Camburn et al. 1978: figs 14: 210–214) is even smaller (L= 12–16.5 µm; B= 2–3 µm) and the axial and central areas are indistinct. Gomphosphenia reicheltii (M.Schmidt) Lange-Bertalot (1995) has distinctly punctate striae and lanceolate axial area in larger specimens and very narrow axial area in smaller specimens. There are probably two different species illustrated as Gomphonema reicheltii M. Schmidt in Schmidt (1899 in Schmidt 1874 – 1959: figs 214: 19–22); the valves depicted in figs 214: 19, 20 significantly differ in valve shape and shape of the central area from the valves illustrated in figs 214: 21, 22. However, detailed observation of type material is warranted for establishing the proper identity of both populations. Gomphosphenia oahuensis (Hustedt) Lange-Bertalot (in Moser et al. 1998) has isopolar valves with slightly protracted ends, in contrast to the narrowly-clavate valves in G. tenuis. Even larger differences can be observed with SEM in respect to raphe structure (compare with Moser 1998: figs 5: 6–8, figs 53: 1–9). Gomphosphenia stoermeri Kociolek & E.W.Thomas (in Thomas et al. 2009) has smaller (L= 10–20.1 µm) and narrower (B= 1.5–3.1 µm) valves with a higher striae density (S= 28–35); the striae are composed of elongated areolae which extend to the raphe slits. These characters make differentiation between G.stoermeri and G. tenuis simple. Gomphonema brasiliense Grunow (1878: 110) and Gomphonema demerarae (Grunow) Frenguelli (1941: fig. 3: 11) should probably be transferred to Gomphosphenia (Krammer & Lange-Bertalot 1985: figs 41: 1–5); both species significantly differ in the valve shape and size from G. tenuis. Genus Gomphonema Agardh (1824), Published as part of Levkov, Zlatko & Williams, David M., 2011, Fifteen new diatom (Bacillariophyta) species from Lake Ohrid, Macedonia, pp. 1-41 in Phytotaxa 30 on pages 20-23, DOI: 10.11646/phytotaxa.30.1.1, http://zenodo.org/record/4894396, {"references":["Lange-Bertalot, H. (1995) Gomphosphenia paradoxa nov. spec. et nov. gen. und Vorschlag zur Losung taxonomischer Probleme infolge eines veranderten Gattungskonzepts von Gomphonema (Bacillariophyceae). Nova Hedwigia 60: 241 - 252.","Lange-Bertalot, H. (1993) 85 neue taxa und uber 100 weitere neu definierte Taxa erganzend zur Susswasserflora von Mitteleuropa, Vol. 2 / 1 - 4. Bibliotheca Diatomologica 27: 1 - 164.","Hustedt, F. 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Taxonomy, ultrastructure and distribution of Gomphonemoid diatoms (Bacillariophyceae) from Great Smoky Mountains National Park (U. S. A.). In: Kociolek, J. P., Theriot, E. C. & Stevenson, R. J. (eds.), Diatom taxonomy, ultrastructure and ecology: modern methods and timeless questions. A tribute to Eugene F. Stoermer. Nova Hedwigia, Beiheft 135: 201 - 237.","Grunow, A. (1878) Algen und Diatomaceen aus dem Kaspischen Meere. In: Schneider, O. (Ed), Naturwissenschafte Beitrage zur Kenntniss der Kaukasuslander, auf Grund seiner Sammelbeute, Dresden: Verlage der Burdach'schen Hofbuchhandlung, pp. 98 - 132.","Frenguelli, J. (1941) Diatomeas del Rio de la Plata. Revista del Museo de la Plata, Nueva Serie, Seccion Botanica 3: 213 - 334.","Krammer, K. & Lange-Bertalot, H. (1985) Naviculaceae Neue und wenig bekannte Taxa, neue Kombinationen und Synonyme sowie Bemerkungen zu einigen Gattungen. Bibliotheca Diatomologica 9: 5 - 230.","Agardh, C. A. (1824) Systema Algarum. Adumbravit C. A. Agardh. 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