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Lake Tanganyika, the second oldest lake in the world, is home to some of the largest and most phenotypically, genetically, and ecologically diverse freshwater assemblages. While the evolutionary processes responsible for generating its extraordinary richness are well understood across various animal groups, little is known about the diatom species richness, turnover patterns, and their drivers. Here, we explored species richness of the diatom genus Diploneis from Lake Tanganyika and surrounding regions by using morphological and molecular information. Both datasets suggested the presence of twenty-five new Diploneis species, each not related to any known Diploneis species so far. The multi-locus phylogeny indicates a monophyletic group of twenty-one Diploneis species from Lake Tanganyika, suggesting potential intralacustrine diversification possibly triggered by certain historical contingencies. This is supported by the small genetic distances and the presence of unique silica ornamentations on the valve face exterior, to date only known to occur on the Baikal endemic Diploneis implicatus. The discovery of such a high richness of Diploneis species in Lake Tanganyika and the presence of a unique morphological character points to a potential adaptive radiation - a mechanism yet to be confirmed.

A new species was discovered in Taihang Valley, Shanxi province, China. It shared the typical characteristics of the genus Chamaepinnularia, such as chambered striae, vela-covered areolae and small frustules. Valves of Chamaepinnularia taihangensis sp. nov. are linear-lanceolate with capitate apices. Valve margins showed distinct triple curvatures in light microscopy. Axial area and central area narrow, rhombic. The new species was compared with the four related taxa, C. hassiaca, C. justa, C. krookiformis and C. soehrensis. These species differed from the new species in valve outline, valve size, stria density and the shape of the central area. The details of the valves as shown by light and scanning electron microscopy are described. This new species occurs in benthic and epiphyte habitats. We discuss the ecological breadth and systematic position of the genus Chamaepinnularia.

Sellaphora tanghongquii sp. nov. is described from epilithic samples taken from river systems in Southern China. The morphology of the new species is described based on light microscopy (LM) and scanning electron microscopy (SEM), and detailed ecological information is provided. This species has diagnostic features consistent with the genus Sellaphora, including small and linear valves, undulate and filiform raphe, and the presence of internal hymenate occlusions. Compared to morphologically similar species, we found that the new species is the most similar to S. constrictum in valve size and outline, raphe structure, and the external arrangement of the striae. However, S. tanghongquii sp. nov. has the following outstanding features which distinguish from similar species: 1) the valve striae are uniseriate externally and biseriate internally, 2) the shape of areolae are mostly square to elliptical, partly round, oval or irregularly shaped, composed of 2–4 small holes inside externally and round, elliptical, C-shaped, or irregularly shaped internally, 3) undulate valves with a slight constriction near the central portion of the valve, and 4) the presence of a row of separated and small pores on the valve mantle. The species appears to be best assigned to the group of species with axial grooves, which includes the generitype of Sellaphora. The discovery of this new diatom species increases the known biodiversity of the southern regions in China.

During a survey of diatoms present in tidal pools on the coasts of Livingston Island (South Shetland Islands), we found several populations, belonging presumably to the Antarctic endemic Craspedostauros laevissimus. Further analyses using light microscopy revealed that the populations show differences in stria density. Following scanning electron microscopy observations, only part of the investigated populations could be assigned to C. laevissimus, whereas the others are sufficiently morphologically different based on stria density and their cribrate areolae structure to be described as a new species: Craspedostauros confusus sp. nov. The new taxon is compared with known, morphologically similar, Craspedostauros taxa. The paper presents morphological and ecological data for both taxa discussed in the study. A detailed survey of the early Antarctic literature showed that the Craspedostauros taxa in Antarctica have convoluted taxonomic histories and that the new taxon has likely been hidden for long within the variability of C. laevissimus.

Microcostatus labrisicus sp. nov., a terrestrial species, is described from mosses growing on concrete flower beds in Gaharu Park (Sambas city, Borneo Island). Its morphology was studied with light and scanning electron microscopy revealed a set of unique morphological features. The new species differs from all other Microcostatus species by having an unusual arrangement of longitudinal depressions, positioned on both sides of sternum. They are separated by thickened fascia with the shape of a symmetric double-headed axe. A detailed morphological comparison taxa with similar morphological characteristics and additional information on the associated diatom flora is also provided.

Navicula fuxianturriformis sp. nov., collected from Lake Fuxian, Yunnan Province, China, is described as a new species based on light and scanning electron microscope observations. N. fuxianturriformis sp. nov. has lineolate areolae closed by hymenes internally and a peculiar structure of the raphe system where the raphe is elevated internally on a thin longitudinal rib that is laterally expanded at the central area; features that assign it to the genus Navicula. The key diagnostic features of this new species include: 1) lanceolate valves with the cuneate to apiculate apices, 2) mostly long, slit-like, partly round-rectangular areolae on the valve exterior and round to rectangular areolae internally, 3) external distal raphe fissures that are hooked opposite one another, and 4) the oval-elliptical central area, with two to five pairs of irregularly shortened striae. This combination of features distinguishes N. fuxianturriformis from congers such as N. turriformis, N. turris, N. reinhardtii, N. hoevsgoelreinhardtii, N. mongolreinhardtii, N. apiculatoreinhardtii or N. apiculatoreinhardtii f. biseriata. A discussion of the morphological features of this taxon and morphologically-similar species is presented. These findings increase our understanding about the morphology and distribution of the genus Navicula in China.

Adlafia kociolekii C.Radhakrishnan, Sudipta K.Das, C.E.Wetzel & B.Karthick sp. nov. (Figs 2–43) Description: —LM (Figs 2–28): Valves lanceolate to linear-lanceolate, elliptical, with acute apices: valve length 16– 53.5 μm, width 6–10.5 μm (n=25). Raphe slightly lateral and straight, inflated proximal ends, very slightly deflected to primary side, distal ends deflected in opposite direction. Striae uniseriate, 26–30 in 10 μm, composed of round areolae, radiate at centre, parallel to convergent near apices. Valves with narrow axial area [sternum], central area broad and elliptical in large valves, narrow, straight in smaller ones. Voigt discontinuity is clearly discernible towards both poles. SEM (Figs 29–43): Externally, the raphe system is narrow and not prominent (Figs 29–30). Proximal raphe ends slightly dilated and teardrop-like (Figs 34–35). Hook-like distal ends bend in the opposite direction (Figs 30–33). Uniseriate striae, areolae mostly covered with hymenes, clearly visible only when thoroughly oxidized (Figs 29–31). The shape of the areolae is round to oval near mantle and oval to elongate near axial area. Areolae more regularly arranged on primary side; less regular on secondary side (Fig. 29). Areolae more elongate near the central area (Fig. 34). Internally, raphe is thin and almost straight and the sternum more elevated (Figs 36–37). Distal raphe ends slightly bent, with long raised helictoglossae (Figs 38, 40–41). Proximal raphe ends are deflected in the opposite direction to the distal ends (Fig. 36). Striae form round to elliptical areolae opening on entire valve (Figs. 42–43). Mantle is deep, a rows of areolae is present near to distal ends and terminating with helictoglossae (Fig. 40). Type locality: Panchgotey, Kyongnosla Alpine Sanctuary, Sikkim, India, 27.3197° N, 88.5455° E, 3888 m a.s.l.; attached to moss (epibryophytic) patches on rocks (Agharkar Herbarium of Maharashtra Association (AHMA) #2421, holotype, an example illustrated in Figure 2; Central National Herbarium (CAL), Isotype no. CAL /ALG.60). Etymology: The species name is in the honour of eminent diatomologist Dr John Patrick Kociolek from CU Museum of Natural History, the University of Colorado at Boulder, USA. Ecology and distribution: The type material was aerial in occurrence. The species was also found epilithic in freshwater and in subaerophytic habitats in northeast India. A small population of the taxon was found epipsammic habitat of a stream near Khamrang, Mizoram. Rare occurrences of the taxa were also noted on wet walls in Angori (Meghalaya) and Keitum (Mizoram). The details of the distributions of the taxon in various parts of northeast India, along with the other diatoms growing in consortium, are presented in Table 1., Published as part of Se. Wetzel & Karthick, Balasubramanian, 2023, Adlafia kociolekii sp. nov. (Bacillariophyceae): a new naviculoid diatom from the Eastern Himalayas, India, pp. 62-72 in Phytotaxa 595 (1) on pages 64-66, DOI: 10.11646/phytotaxa.595.1.4, http://zenodo.org/record/7889438

Se.Wetzel, Karthick, Balasubramanian (2023): Adlafia kociolekii sp. nov. (Bacillariophyceae): a new naviculoid diatom from the Eastern Himalayas, India. Phytotaxa 595 (1): 62-72, DOI: 10.11646/phytotaxa.595.1.4, URL: http://dx.doi.org/10.11646/phytotaxa.595.1.4

Diploneis distinctebipunctata sp. nov. (LM Figs 549–560, SEM Figs 561–566) Valves are weakly asymmetric, elliptic-lanceolate becoming elliptic-circular with smaller cell size (Figs 549–561). Valve length is 28–57 μm and width is 18–26 μm. The axial area is narrow, linear to lanceolate, patterned with irregular round ornamentations opening into small depressions that do not penetrate the silica cell wall (white arrow Fig. 562). The axial area slightly widens into a longitudinally elongate and weakly asymmetric central area (Figs 549, 561, 565), 3–6 μm wide. Externally, the canal is linear to lanceolate, slightly expanded in the middle of the valve with two (three) rows of cribrate (>40 poroids) areolae narrowing into one larger at the valve apices (Figs 549–552, 561). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Fig. 566). Externally, the raphe is filiform, curved; the proximal ends are deflected to one side within expanded teardrop depressions (Figs 561, 565). The distal raphe ends are unilaterally bent to the same side as the proximal ends and terminate on the upper section of the mantle (Figs 561, 562). Internally, the raphe is curved and placed in the depression formed by the longitudinal canal (Fig. 566). The striae are parallel at mid-valve becoming radiate towards the apices, 8–10 in 10 μm. Striae are biseriate throughout (Figs 563, 564). The striae are composed of round areolae covered externally with fine pored cribra (>40 poroids), 15–18 in 10 μm. Internally, the alveoli open via a single elongated opening covered with a thin silica layer (Figs 564, 566). The valvocopula has serrated advalvar edges (Fig. 566). Type:— REPUBLIC OF ZAMBIA, Mulungushi River, at 1117 m elevation; mud, 0.1 m water depth, 14°17’45.6” S 28°32’54.8” E, E. Jovanovska & Z. Levkov, 27 th September 2021 (holotype designated here, circled specimen BM-108976! = Fig. 552, isotypes ANSP-GC17205!, CANA-130011!). Type material CANA-129322. Registration: http:// phycobank.org/103705 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S 3m). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660300). Etymology:— The specific epithet ‘ distinctebipunctata ’ refers to the visible biseriate nature of the striae under LM observation. Ecology and distribution:— This species has only been observed in the Mulungushi River and Kalambo River and in the fossil deposits of Lake Malawi (unpublished data). The Mulungushi River, from where this species was described, has a moderately alkaline pH (7.9), a low conductivity of 101 μS̔ cm-1, and low water transparency. It cohabits with the species Diploneis dissipata sp. nov. and Diploneis latissima sp. nov. Main differential characters:— Valve width and shape, striae pattern, narrow canals, surface depressions along axial area, and poroids>40 per areola. Similar species:— Diploneis lusatica and Diploneis amicula Kulikovskiy & Lange-Bertalot (2015: 86)., Published as part of Jovanovska, Elena, Wilson, Mallory C., Hamilton, Paul B. & Stone, Jeffery, 2023, Morphological and molecular characterization of twenty-five new Diploneis species (Bacillariophyta) from Lake Tanganyika and its surrounding areas, pp. 1-102 in Phytotaxa 593 (1) on page 83, DOI: 10.11646/phytotaxa.593.1.1, http://zenodo.org/record/7875089, {"references":["Kulikovskiy, M. S., Lange-Bertalot, H. & Kuznetsova, I. V. (2015) Lake Baikal: hotspot of endemic diatoms II. Iconographia Diatomologica 26: [1] - 656."]}

Diploneis latissima sp. nov. (LM Figs 567–576, SEM Figs 577–581) Valves are weakly asymmetric, elliptic-lanceolate with convex margins and round ends (Figs 567–577). Valve length is 31.5–48.5 μm and width is 23–29.5 μm. The axial area is narrow, linear to lanceolate (Fig. 568), patterned with irregular round ornamentations opened into small depressions that do not penetrate the silica cell wall (white arrow in Fig. 577). The axial area slightly widens into a longitudinally elongate and weakly asymmetric central area, 3.8–5.5 μm wide. Externally, the canal is linear to lanceolate, slightly expanded in the middle of the valve with two to three rows of cribrate areolae narrowing into one larger at the valve apices (Fig. 577). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Fig. 580). Externally, the raphe is filiform with slightly arched branches (Fig. 577). The distal raphe ends are unilaterally bent (Fig. 577). The raphe system is from the outside followed by irregularly positioned roundish structures located between the raphe and the row of areolae (white arrow in Fig. 577). Internally, the raphe is curved and placed in the depression formed by the longitudinal canal (Fig. 580). The striae are parallel at mid-valve becoming radiate towards the valve apices, 8–9 in 10 μm. Striae are biseriate throughout (Figs 578, 579). The striae are composed of round depressed areolae covered externally with fine pored cribra (ca. 40 poroids), 15–18 in 10 μm. The interstriae are distinct (Fig. 579). Internally, the alveoli open via a single elongate opening covered with a thin silica layer (Fig. 581). The valvocopula has serrated advalvar edges (Fig. 580). Type:— REPUBLIC OF ZAMBIA, Mulungushi River, at 1117 m elevation; mud, 0.1 m water depth, 14°17’45.6” S 28°32’54.8” E, E. Jovanovska & Z. Levkov, 27 th September 2021 (holotype designated here, circled specimen BM-108975! = Fig. 575, isotypes ANSP-GC17204!, CANA-129322!). Type material CANA-129322. Registration: http:// phycobank.org/103711 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S3n). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660299) and nuclear encoded 18S (SSU rDNA) sequence (GenBank accession: OQ 629558). Etymology:— The specific epithet ‘ latissima ’ refers to the broad width of the valve. Ecology and distribution:— This species was observed only in the Mulungushi River, which has a moderately alkaline pH (7.9), a low conductivity of 101 μS̔ cm-1, and low water transparency. It coexists with Diploneis dissipata sp. nov. and D. distinctebipunctata sp. nov. Main differential characters:— Valve width and shape, striae pattern, areolae offset, poroids ca. 40 per areola. Similar species:— Diplonies sanantoniensis Lange-Bertalot & Fuhrmann (2020: 123) and Diploneis dilatatafalsa Lange-Bertalot & Fuhrmann (2020: 36).

Diploneis gigantea sp. nov. (LM Figs 73–78, SEM Figs 79–84) Valves are weakly asymmetric, linear-elliptic with slightly convex margins and round ends (Figs 73–79). Valve length is 67–106.5 μm and valve width is 37.5–46 μm. The axial area is narrow, expanding towards the narrow, lanceolate and weakly asymmetric central area (Figs 73, 80), 6–8 μm wide. Externally, the longitudinal canal is broad, lanceolate to linear, slightly expanded in the middle of the valve with four rows of cribrate areolae (10–15 poroids) narrowing into one at the valve apices (Figs 73–78, 80, 81). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Fig. 83). Externally, the raphe is filiform, curved with proximal ends positioned within expanded teardrop depressions (Figs 79, 80). The distal raphe ends are unilaterally bent to the same side as the proximal ends and terminate at the valve face margin (Figs 79, 81). Internally, the raphe is curved with simple proximal and distal ends that are slightly elevated in a deep depression formed by the longitudinal canal (Figs 82, 83, 84). The striae are parallel at mid-valve becoming radiate towards the valve apices, 7–8 in 10 μm. Striae are uniseriate throughout (Figs 79, 81). The striae are composed of small round to rectangular areolae covered with cribra (>30 poroids), 7–8 in 10 μm. Each areola opens in a depression slightly lower than the non-porous valve surface. The inter-areolar thickenings have crested fin-like ridge silica ornamentations, which are serrated into ca. 3–5 notched edges (in the illustrated specimens hardly visible but see white arrow in Fig. 81). The stria areolae are divided by thickenings, forming from the areolae wall (white arrow in Fig. 81). Areolae increase in size towards the valve margins (Fig. 81). Internally, the alveoli open via a single elongated opening covered with a thin silica layer (Fig. 82). Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Kalambo Falls Lodge, at 771 m elevation; mud, 18 m water depth, collected SCUBA diving, 8°37’25.6” S 31°11’59.7” E, H. Buescher, 1 th September 2018 (holotype designated here, circled specimen BM-108994! = Fig. 75, isotypes ANSP-GC17223!, CANA-129338!). Type material CANA-129315. Registration: http://phycobank.org/103709 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S2a). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ660290). The sequence comes from an isolated individual from the same area, but on sand in 5 m water depth (Acc. No. 91, Diatom Collection Elena Jovanovska; see coordinates in Table S1). However, as this species is extremely rare, we chose a nearby, deeper site as type material, where the species is more abundant but still very rare. Etymology:— The specific epithet ‘ gigantea ’ refers to the very large cell sizes of this species. Ecology and distribution:— This species has only been observed on the coasts of Tanzania and Zambia in the southern and central sub-basins of Lake Tanganyika. In the alkaline, moderately mineral-rich and highly transparent waters, the species usually inhabits sandy and muddy substrates (sometimes with mollusk shells) between 9 and 26 m water depth. It can also be found on submerged rocks below 20 m water depth and below 9 m water depth, where it is very rare. Diploneis gigantea sp. nov. was found mainly in the southern sub-basin at Kalambo Falls Lodge, Isanga Bay, Mutondwe Island, Cape Nangu at Kasaba Bay, Ndole Bay (Fig. 1c, f) and less frequently in the central sub-basin in Kalya Bay and Mahale National Park (Fig. 1c, e). In all these locations the species is extremely rare, typically one to two (very rarely a handful) specimens are found per slide together with D. salzburgeri sp. nov., D. cocquytiana sp. nov., D. elongata sp. nov., D. tessellata sp. nov., D. fossa sp. nov., and D. cristata sp. nov. Main differential characters:— Large valve size, linear-elliptic valve shape, striae density, and external fin-like ornamentations across the valve. Similar species:— Diploneis fossa sp. nov., Diploneis goohon Kulikovskiy & Lange-Bertalot (2015: 95), and Diploneis obtusa Kulikovskiy & Lange-Bertalot (2015: 99).

Diploneis tessellata sp. nov. (LM Figs 132–141, SEM Figs 142–151) Valves are weakly asymmetric, broadly elliptic with convex margins and bluntly round ends (Figs 132–143). Valve length is 29.5–60.5 μm and valve width is 18.5–33.5 μm. The axial area is narrow, lanceolate, widening at the center to form an elongate and weakly asymmetric central area (Figs 133, 145, 146), 3.5–6.5 μm wide. Externally, the canal is linear to lanceolate, slightly expanded in the middle of the valve with three rows of cribrate ( Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Kalambo Falls Lodge, at 770 m elevation; mud, 18 m water depth, collected SCUBA diving, 8°37’25.6” S 31°11’59.7” E, H. Büscher, 1 st September 2018 (holotype designated here, circled specimen BM-108986! = Fig. 138, isotypes ANSP-GC17215!, CANA-129336!). Type material CANA-129315. Registration: http://phycobank.org/103720 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S 3t). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660296) and nuclear encoded 18S (SSU rDNA) sequence (GenBank accession: OQ 629557). Etymology:— The specific epithet ‘ tessellata ’ refers to the blocky, tiled appearance of the areolae of this species. Ecology and distribution:— This species has only been observed in Lake Tanganyika along the coasts of Zambia and Tanzania in the three sub-basins, especially in Kalambo Falls Lodge, Isanga Bay, Mutondwe Island, Kalya Bay, Rukoma area, and Kiganza Bay (see Fig. 1c–f). The species is not very abundant in the alkaline, moderately mineral-rich and highly transparent waters and occurs in sandy and muddy substrates (sometimes with mollusk shells) between 10 and 33 m water depth. It can also be found on submerged rocks in the littoral areas at Jakobsen Beach, at 5 m depth on Buhingu Island, and at 20 m depth in Isanga Bay, probably due to upwelling, currents, and/or turbidity. Diploneis tessellata sp. nov. occurs together with D. salzburgeri sp. nov., D. cristata sp. nov., D. gigantea sp. nov., D. fossa sp. nov., D. cocquytiana sp. nov., D. kilhamiana sp. nov., D. tanganyikae sp. nov., and D. serrulata sp. nov. Main differential characters:— Valve shape, striae density, areolae density, external thick fin-like ornamentations evenly distributed across the valve, and poroids 25–45 per areola. Similar species:— Diploneis tenera sp. nov., D. cristata sp. nov., and D. elliptica.

Diploneis salzburgeri Jovanovska sp. nov. (LM Figs 2–11, SEM Figs 12–23) Valves are weakly asymmetric, broadly lanceolate to weakly rhombic-elliptic becoming circular with smaller cell size (Figs 2–11). Valve length is 53.5–100.5 μm and valve width is 34.5–54.5 μm. The axial area is narrow and only slightly expanded close to the central area (Fig. 14); patterned with irregular round ornamentations opening into small depressions that do not penetrate the silica cell wall (white arrow Fig. 17). The central area is longitudinally elongate, 5.5–8.5 μm wide. Externally, the longitudinal canal is broad, lanceolate to linear, slightly expanded in the middle of the valve with four (rarely five to six) rows of cribrate areolae (>20 poroids) narrowing into two to one at the valve apices (Figs 12–14, 16). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canals (Figs 18, 21). Externally, the raphe is filiform, curved; the proximal ends are simple and weakly curved to one side, and positioned within an expanded teardrop depression (Figs 13, 14, 17). The distal raphe ends are unilaterally bent to the same side as the proximal ends and terminate at the junction of the valve face and mantle (Figs 12, 13, 16). Internally, the raphe is curved with simple proximal and distal ends that are slightly elevated in a deep depression formed by the longitudinal canal (Figs 18–20, 23). The striae are parallel at mid-valve becoming radiate towards the valve apices, 8–10 in 10 μm. Striae are uniseriate throughout (Fig. 15). Externally, the striae are composed of small complex round to rectangular areolae covered with cribra (>20 poroids), 5–8 in 10 μm. Each stria and canal areola opens into a depression slightly lower than the rest of the non-porous valve surface, divided (typically in four) by narrow thickened bars that bear small fin-like silica ridges (white arrowed Fig. 15). The stria areolae are also divided by robust thickenings that form from the areolae walls (white arrowed Fig. 16). A few areolae are covered partially or entirely by thin flaps of silica, forming from the areolae walls (black arrowed Fig. 16). The inter-areolar thickenings bear transapical and longitudinal ridge-like shaped silica ornamentations serrated into ca. 4–7 notched edges (white arrowed Fig. 14). The areolae increase in size towards the valve margins (Figs 12, 15). Internally, the alveoli open via a single elongated opening covered with a thin silica layer (Figs 18, 22). Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Ndole Bay, at 768 m elevation; mud, 12 m water depth, collected SCUBA diving, 8°28’34.7” S 30°27’06.7” E, W. Salzburger, 30 th September 2021 (holotype designated here, circled specimen BM-108978! = Fig. 7, isotypes ANSP-GC17207!, CANA-129323!). Type material CANA-129323. Registration: http://phycobank.org/103716 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S2b). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660289) and nuclear encoded 18S (SSU rDNA) sequence (GenBank accession: OQ 629559). Etymology:— The specific epithet ‘ salzburgeri ’ was given in honor of Prof.Walter Salzburger, who has contributed significantly to the understanding of cichlid fish evolution in Lake Tanganyika and who collected the type material. Ecology and distribution:— This species has been observed in Lake Tanganyika along the coasts of Zambia and Tanzania (including the coast of Burundi; Cocquyt 1998, fig. 14: 2). It typically inhabits the sandy and muddy stretches between 6 and 33 m water depth in the southern, central, and northern parts of this alkaline lake with moderate mineral content and high-water transparency. It can also be found free-living (i.e. tychoplanktonic) or on submerged rocks, fishing nets, and other objects probably due to water currents and turbulence. Considering the robust and large size of Diploneis salzburgeri sp. nov., the species is not very abundant, but it is widespread and usually occurs together with D. cristata sp. nov., D. gigantea sp. nov., D. fossa sp. nov., D. major sp. nov., D. kilhamiana sp. nov., D. tessellata sp. nov., D. tanganyikae sp. nov., D. serrulata sp. nov., and D. cocquytiana sp. nov. in Isanga Bay, Chituta Bay, Mutondwe Island, Kalambo Falls Lodge, Ndole Bay, Cape Nangu at Kasaba Bay, Kalya Bay, Jakobsen Beach near Kigoma, Buhingu Island, and Mahale National Park (see Fig. 1c–f). Main differential characters:— Valve size and shape, external fin-like ornamentations across the valve, patterned axial area, areolae with fin-like extensions, and poroids>20 per areola. Similar species:— Diploneis tanganyikae sp. nov., Diploneis cristata sp. nov., Diploneis major sp. nov., and Diploneis erwin-reichardtii Lange-Bertalot, Fuhrmann & Werum (2020: 43). Taxonomic note:— Diploneis salzburgeri sp. nov. is very variable in the shape of the valves. Individuals ranging from narrowly elliptical to widely elliptical or even rhombic can be observed within and between populations. The nature of these different shapes and the causes of shape variation remain to be investigated, preferably by wholegenome sequencing. However, since our genetic data based on two markers and the morphometric data do not show a clear separation, we have considered these variations as conspecific. Morphological variations of this nature have also been observed in other robust Diploneis species, such as Diploneis hoevsgoelensis Jovanovska, Levkov & Edlund (2015: 206) (Jovanovska et al. 2015) and Diploneis alpina Meister (1912: 103) (Jovanovska et al. 2013).

Diploneis major sp. nov. (LM Figs 61–66, SEM Figs 67–72) Valves are weakly asymmetric, broadly elliptic to rhombic-elliptic becoming elliptic-circular with smaller cell size (Figs 61–67). Valve length is 30–62.5 μm and valve width is 21.5–37 μm. The axial area is narrow, linear to lanceolate, expanding into the longitudinally elongate and weakly asymmetric central area (Figs 61, 68), 3.7–6.5 μm wide. Externally, the longitudinal canal is broad, lanceolate to linear, slightly expanded in the middle of the valve with three to four rows of cribrate (8–12 poroids) areolae narrowing into two to one at the valve apices (Figs 67, 68). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Fig. 70). Externally, the raphe is filiform, curved with proximal fissures positioned within shallow teardrop depressions; the fine terminal fissures are bent to the same side of the valve and terminate on the valve face at the mantle (Figs 67–69). Internally, the raphe is curved with simple proximal and distal ends that are slightly elevated in a deep depression formed by the longitudinal canal (Figs 70–72). The striae are parallel at mid-valve becoming radiate towards the valve apices, 8–9 in 10 μm. Striae are uniseriate throughout (Fig. 67). The striae are composed of small complex round to rectangular areolae covered with cribra (>40 poroids), 9–10 in 10 μm (Fig. 68). The cribra has a volae-like shape that could be a real structure or the result of corrosion (white arrow in Fig. 68). Each areola opens into deep pits and it is divided by narrow thickened bars that bear small crested fin-like ridge silica ornamentations (Fig. 67). The crested fin-shaped silica ornamentations are serrated into ca. 3–5 notched edges (Fig. 68). The areolae increase in size towards the valve margins (Fig. 67). Internally, the alveoli open via a single elongated opening covered with a thin silica perforated layer (white arrow in Fig. 72). Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Isanga Bay, at 768 m elevation; rock scrape, 20 m water depth, collected SCUBA diving, 8°39’10.7” S 31°11’34.8” E, A. Jordan, 8 th October 2021 (holotype designated here, circled specimen BM 108983! = Fig. 65, isotypes ANSP-GC17212!, CANA-129329!). Type material CANA-129329. Registration: http://phycobank.org/103714 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S2d). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660283). Etymology:— The specific epithet ‘ major ’ is refers to the species great size. Ecology and distribution:— This species has only been observed on the Tanzanian and Zambian coasts of Lake Tanganyika. It is a rather rare and not very frequent species in the alkaline, moderately mineral waters, occurring mainly in the southern sub-basin on sand at 15 to 36 m water depth and on sand craters formed by cichlids and rarely on mud at more than 30 m depth. We found it particularly in Isanga Bay, Chituta Bay, Mutondwe Island, and at Cape Nangu in Kasaba Bay (Fig. 1c, f). Fewer individuals were also found in the central sub-basin in Kalya Bay and Mahale National Park (Fig. 1c, e). In both sub-basins, the species is mostly found together with D. fossa sp. nov., D. salzburgeri sp. nov., D. tumida sp. nov., D. gigantea sp. nov., and D. serrulata sp. nov. Main differential characters:— Valve shape, external fin-like ornamentations across the valve, fin-like formations within areolae, cribra with volae-like shape, and highly recessed areolae over the longitudinal canals. Similar species:— Diploneis salzburgeri sp. nov. and Diploneis baicaloparma Kulikovskiy & Lange-Bertalot (2015: 89)., Published as part of Jovanovska, Elena, Wilson, Mallory C., Hamilton, Paul B. & Stone, Jeffery, 2023, Morphological and molecular characterization of twenty-five new Diploneis species (Bacillariophyta) from Lake Tanganyika and its surrounding areas, pp. 1-102 in Phytotaxa 593 (1) on page 20, DOI: 10.11646/phytotaxa.593.1.1, http://zenodo.org/record/7875089, {"references":["Kulikovskiy, M. S., Lange-Bertalot, H. & Kuznetsova, I. V. (2015) Lake Baikal: hotspot of endemic diatoms II. Iconographia Diatomologica 26: [1] - 656."]}

Diploneis kilhamiana sp. nov. (LM Figs 349–372, SEM Figs 373–383) Valves are weakly asymmetric, linear-elliptic with parallel to weakly convex margins and round apices (Figs 349–373). Valve length is 22.5–43 μm and width is 11.5–15 μm. The axial area is linear to lanceolate, widening at the center to form a small lanceolate central area (Figs 351, 373, 376), 2.5–3.5 μm wide. Externally, the canal is linear to lanceolate, slightly expanded in the middle of the valve with two rows of cribrate (8–15 poroids) areolae narrowing into one at the valve apices (Figs 351, 373, 375). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Figs 379, 381). Externally, the raphe is filiform, curved with expanded proximal ends weakly deflected to one side; the proximal ends are positioned within an elongated teardrop depression (Figs 373, 375, 376). The distal raphe ends are unilaterally bent to the same side and terminate as expanded pores at the valve face margin (Figs 374, 375, 377). Internally, the raphe is curved with simple proximal and distal ends that are slightly elevated in a depression formed by the longitudinal canal (Figs 380, 381, 383). The striae are parallel at mid-valve becoming radiate towards the apices, 9–11 in 10 μm. Striae are biseriate throughout (Figs 378, 379, 382). The striae are composed of round to rectangular areolae covered externally with fine pored cribra (15–20 poroids), 20 in 10 μm. The inter-areolar thickenings have fin-like silica ridges serrated with ca. 8–10 notched edges (Fig. 374). The fin-like silica ornamentations along the canal are slightly bent into a semi-circular shape, positioned towards the striae whereas those of the striae are only slightly bent towards the canal and change direction only at the valve mantle (Figs 374–376). The areolae increase in size towards the valve margins (Fig. 378). Internally, the alveoli open via a single elongated opening covered with a thin silica layer (Figs 380–382). The valvocopula has serrated advalvar edges (Figs 379–382). Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Kalambo Falls Lodge, at 770 m elevation; mud, 18 m water depth, collected SCUBA diving, 8°37’25.6” S 31°11’59.7” E, H. Büscher, 1 st September 2018 (holotype designated here, circled specimen BM-108985! = Fig. 370, isotypes ANSP-GC17214!, CANA-129335!). Type material CANA-129315. Registration: http://phycobank.org/103710 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S3v). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660280). Etymology:— The specific epithet ‘ kilhamiana ’ honors Dr. Susan S. Kilham, who made many contributions to the field of diatom ecology, including research in Lake Tanganyika. Ecology and distribution:— This species has been observed in Lake Tanganyika, where the water is predominantly alkaline, moderately mineral-rich and very transparent. The species is widespread in the southern, central, and northern sub-basins on the Tanzanian and Zambian sides (including Burundi, see Cocquyt 1999, fig. 16), especially at Kalambo Falls Lodge, Cape Nangu in Kasaba Bay, Mahale National Park, Kiganza Bay, as well as Isanga Bay, Chituta Bay, and the Rukoma area (see Fig. 1c–f). Diploneis kilhamiana sp. nov. inhabits sandy and muddy substrates (sometimes with mollusk shells) between 10 and 36 m water depth. A few specimens were found in 70 m water depth in the cleaned samples from Chituta Bay, and live specimens were found on the submerged rocks in the coastal areas at Jakobsen Beach near Kigoma, probably due to sediment distribution caused by currents and water turbulence at both sites. This species normally coexists with D. cocquytiana sp. nov., D. gigantea sp. nov., D. salzburgeri sp. nov., D. tenera sp. nov., D. nana sp. nov., D. fossa sp. nov., D. angusta sp. nov., and D. cristata sp. nov. Main differential characters:— Valve shape, striae pattern, and external thick fin-like ornamentations across the valve; fins more randomly distributed across the canals. Similar species:— Diploneis cocquytiana sp. nov., Diploneis heteromorphiforma Metzeltin, Lange-Bertalot & Nergui (2009: 35), and Diploneis pseudovalis Hustedt (1930: 253)., Published as part of Jovanovska, Elena, Wilson, Mallory C., Hamilton, Paul B. & Stone, Jeffery, 2023, Morphological and molecular characterization of twenty-five new Diploneis species (Bacillariophyta) from Lake Tanganyika and its surrounding areas, pp. 1-102 in Phytotaxa 593 (1) on page 59, DOI: 10.11646/phytotaxa.593.1.1, http://zenodo.org/record/7875089, {"references":["Cocquyt, C. (1999) Diatoms from a hot spring in Lake Tanganyika. Nova Hedwigia 68: 425 - 439. https: // doi. org / 10.1127 / nova. hedwigia / 68 / 1999 / 425","Hustedt, F. (1930) Bacillariophyta (Diatomeae) Zweite Auflage. In: Die Susswasser-Flora Mitteleuropas. Heft 10. (Pascher, A. Eds), pp. [i] - vii, [1] - 466. Jena: Verlag von Gustav Fischer."]}

Diploneis nana sp. nov. (LM Figs 299–319, SEM Figs 320–322) Valves are weakly asymmetric, linear-elliptic to elliptic with weakly convex margins and slightly acute apices (Figs 299–320). Valve length is 17.5–32.5 μm and valve width is 8.5–11.5 μm. The axial area is very narrow, linear to lanceolate, widening into a slightly longitudinally elongate to indistinguishable and weakly asymmetric central area (Figs 300, 320, 322), 1.5–2.7 μm wide. Externally, the canal is linear to lanceolate, slightly expanded in the middle of the valve with two (rarely three) rows of cribrate (9–15 poroids) areolae narrowing into one at the valve apices (Fig. 320). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Fig. 321). Externally, the raphe is filiform, curved with strongly deflected and expanded proximal ends. The proximal raphe ends are positioned within an elongated surface depression (Fig. 322). The distal raphe ends are unilaterally bent to the same side and extend onto the mantle (Fig. 320). Internally, the raphe branches are slightly arched with simple proximal and distal ends that are slightly elevated in a depression formed by the longitudinal canal (Fig. 321). The striae are parallel at mid-valve becoming radiate towards the apices, 11–13 in 10 μm. Striae are uniseriate throughout (Figs 320, 322). The striae are composed of round areolae covered externally with fine pored cribra (20–33 poroids), 20 in 10 μm. The inter-areolar thickenings have scattered fin-like silica ridges serrated with ca. 4–5 notched edges. The areolae increase in size towards the valve margins (Fig. 320). Internally, the alveoli open via a single elongated opening covered with a thin silica layer (Fig. 321). Type:— UNITED REPUBLIC OF TANZANIA, Lake Tanganyika, Mahale National Park, at 780 m elevation; sand, 30 m water depth, collected SCUBA diving, 6°10’25.1” S 29°44’25.2” E, W. Salzburger, 28 th June 2019 (holotype designated here, circled specimen BM-108996! = Fig. 306, isotypes ANSP-GC17225!, CANA-129317!). Type material CANA-129317. Registration: http://phycobank.org/103715 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S3w). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660277). Etymology:— The specific epithet ‘ nana ’ or dwarf highlights relatively small size of this taxon among Diploneis species in Lake Tanganyika. Ecology and distribution:— This species has only been observed in Lake Tanganyika in the three sub-basins on the Tanzanian and Zambian sides. Despite its small size, this species is never abundant in the alkaline, moderately mineral-rich and highly transparent lake. It is typically found on sandy substrates (sometimes with mollusk shells) or submerged rocks between 9 and 36 m water depth. It is mainly found in Mahale National Park, but also in Kiganza Bay in the north and in Isanga Bay, Mutondwe Island, and Cape Nangu at Kasaba Bay in the south. The small species usually occurs together with D. kilhamiana sp. nov., D. cocquytiana sp. nov., D. salzburgeri sp. nov., D. disjuncta sp. nov., D. clara sp. nov., D. serrulata sp. nov., and D. cristata sp. nov. Main differential characters:— Valve size and shape, central area, external fin-like ornamentations across the valve, and recessed areolae over the canals. Similar species:— Diploneis disjuncta sp. nov. and Diploneis nevrovae Lange-Bertalot & Fuhrmann (2020: 89)., Published as part of Jovanovska, Elena, Wilson, Mallory C., Hamilton, Paul B. & Stone, Jeffery, 2023, Morphological and molecular characterization of twenty-five new Diploneis species (Bacillariophyta) from Lake Tanganyika and its surrounding areas, pp. 1-102 in Phytotaxa 593 (1) on page 54, DOI: 10.11646/phytotaxa.593.1.1, http://zenodo.org/record/7875089, {"references":["Lange-Bertalot, H., Fuhrmann, A. & Werum, M. (2020) Freshwater Diploneis: species diversity in the Holarctic and spot checks from elsewhere. In: Lange-Bertalot, H. (Ed.) Diatoms of Europe. Diatoms of European inland water and comparable habitats. Freshwater Diploneis Two studies, Glashutten: Koeltz Botanical Books. pp. 1 - 526, 691 - 699."]}

Diploneis elongata sp. nov. (LM Figs 442–456, SEM Figs 457–461) Valves are weakly asymmetric, elliptical to linear–elliptical with parallel margins and bluntly round apices (Figs 442– 457). The length of the valve is 30–50 μm and the width is 17–20 μm. The axial area is narrow, lanceolate, widening at the center to form a longitudinally elongate and weakly asymmetric central area (Figs 442, 457, 458), 3.4–4.4 μm wide. Externally, the longitudinal canal is lanceolate, slightly expanded in the middle of the valve with three rows of large cribrate (5–7 poroids) areolae narrowing into one at the valve apices (Figs 443, 457, 458, 460). Externally, the raphe is filiform, curved with straight to weakly deflected proximal ends lying within linearly expanded teardrop depressions (Figs 457, 458). The distal raphe ends are unilaterally bent to the same side as the proximal ends and terminate on the valve face (Figs 457, 461). The striae are parallel at mid-valve becoming radiate towards the valve apices, 9–10(11) in 10 μm. Striae are biseriate throughout (white arrow in Fig. 458). The striae are composed of round areolae covered externally with cribra (8–15 poroids), 15–18 in 10 μm. The inter-areolar thickenings have fin-like silica ridges serrated with ca. 6 notched edges (Fig. 459). The fin-like ornamentations are evenly distributed across the valve and on the canal are bent into semi-circular shapes, positioned towards the striae whereas those of the striae are only slightly bent towards the canal, changing opposite direction only at valve mantle (Figs 457, 458, 461). The areolae increase in size towards the valve margins (Figs 458, 459). Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Kalambo Falls Lodge, at 784 m elevation; sand from fish crater, 7.5 m water depth, collected SCUBA diving, 8°37’22.9” S 31°12’01.8” E, W. Salzburger, 29 th September 2021 (holotype designated here, circled specimen BM-108980! = Fig. 456, isotypes ANSP-GC17209!, CANA-129325!). Type material CANA-129325. Registration: http://phycobank.org/103707 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S3o). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660287). Etymology:— The specific epithet ‘ elongata ’ refers to the elongated shape of the valves. Ecology and distribution:— Diploneis elongata sp. nov. has been observed in Lake Tanganyika in the three sub-basins on the Zambian and Tanzanian side. In the alkaline, moderately mineral-rich and highly transparent waters, the species occurs in relatively large numbers on mud and sand as well as on sand fish craters between 8 and 33 m water depth, especially at Kalambo Falls Lodge, Isanga Bay, Cape Nangu in Kasaba Bay, Mahale National Park, and Kiganza Bay (see Fig. 1c–f). At all sites D. elongata sp. nov. usually occurs together with D. fossa sp. nov., D. serrulata sp. nov., D. kilhamiana sp. nov., D. cocquytiana sp. nov., D. cristata sp. nov., D. clara sp. nov., D. salzburgeri sp. nov., and D. gigantea sp. nov. Main differential characters:— Valve shape, striae pattern, narrow canals, external fin-like ornamentations across the valve, and poroids Similar species:— Diploneis cocquytiana sp. nov. and Diploneis hinziae Lange-Bertalot & Fuhrmann (2016: 163).

Diploneis angusta sp. nov. (LM Figs 323–343, SEM Figs 344–348) Valves are weakly asymmetric, linear-elliptic with parallel to weakly convex margins and round apices (Figs 323– 345). Valve length is 28–48 μm and width is 11–14.5 μm. The axial area is linear to lanceolate, widening at the center to form a longitudinally elongate and weakly asymmetric central area (Figs 326, 345, 348), 2.3–4 μm wide. Externally, the canal is covered with two rows of cribrate (ca. 10 poroids) areolae narrowing into one at the valve apices (Fig. 345). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Fig. 346). Externally, the raphe is filiform, curved with expanded proximal ends deflected to one side; the proximal ends are positioned within an elongated depression (Figs 344, 345, 348). The distal raphe ends are unilaterally bent to the same side and terminate on the valve face at the mantle (Fig. 345). Internally, the raphe is curved with simple proximal and distal ends that are slightly elevated in a deep depression formed by the longitudinal canal (Fig. 346). The striae are parallel at mid-valve becoming radiate towards the apices, 10–12 in 10 μm. Striae are uniseriate throughout (white arrow in Fig. 347). The striae are composed of round areolae covered externally with fine pored cribra (>35 poroids), 15–20 in 10 μm. Inter-areolar thickenings at mid-valve (not ends) have scattered fin-like silica ridges serrated with ca. 4–7 notched edges (Fig. 347). The areolae increase in size towards the valve margins (Figs 345, 347). Internally, the alveoli open through a single elongated opening, typically closed by silica, which is corroded in the illustrated specimen (Fig. 346). The valvocopula has serrated advalvar edges (Fig. 346). Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Cape Nandu, Kasaba Bay, at 768 m elevation; sand and mud, 20 m water depth, collected with Van Veen grab sampler, 8°30’18.9” S 30°38’32.3” E, E. Jovanovska, 2 nd October 2021 (holotype designated here, circled specimen BM-108993! = Fig. 331, isotypes ANSP-GC17222!, CANA-130010!). Type material CANA-129326. Registration: http://phycobank.org/103698 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S2k). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660295). Etymology:— The specific epithet ‘ angusta ’ refers to the narrow shape of the valve. Ecology and distribution:— This species has only been observed in Lake Tanganyika, which is an alkaline, moderately mineral-rich and very transparent system. The species is widespread in the southern, central, and northern sub-basins on the Tanzanian and Zambian sides, especially in Ndole Bay and Cape Nangu in Kasaba Bay, as well as in Isanga Bay, Kalambo Falls Lodge, Mahale National Park, Kiganza Bay, and the Rukoma area (Fig. 1c–f). At all these sites it occurs on sandy (sometimes sandfish nests) and muddy substrates between 10 and 25 m water depth, typically together with D. serrulata sp. nov., D. cocquytiana sp. nov., D. gigantea sp. nov., D. salzburgeri sp. nov., D. kilhamiana sp. nov., D. disjuncta sp. nov., and D. clara sp. nov. Main differential characters:— Valve shape, striae pattern, narrow canals, recessed areolae over the canals, external fin-like ornamentations across the valve, and poroids>35 per areola. Similar species:— Diploneis clara sp. nov., Diploneis calcifuga Lange-Bertalot & Fuhrmann (2020: 28), and Diploneis altana Kulikovskiy & Lange-Bertalot (2015: 86)., Published as part of Jovanovska, Elena, Wilson, Mallory C., Hamilton, Paul B. & Stone, Jeffery, 2023, Morphological and molecular characterization of twenty-five new Diploneis species (Bacillariophyta) from Lake Tanganyika and its surrounding areas, pp. 1-102 in Phytotaxa 593 (1) on page 56, DOI: 10.11646/phytotaxa.593.1.1, http://zenodo.org/record/7875089, {"references":["Lange-Bertalot, H., Fuhrmann, A. & Werum, M. (2020) Freshwater Diploneis: species diversity in the Holarctic and spot checks from elsewhere. In: Lange-Bertalot, H. (Ed.) Diatoms of Europe. Diatoms of European inland water and comparable habitats. Freshwater Diploneis Two studies, Glashutten: Koeltz Botanical Books. pp. 1 - 526, 691 - 699.","Kulikovskiy, M. S., Lange-Bertalot, H. & Kuznetsova, I. V. (2015) Lake Baikal: hotspot of endemic diatoms II. Iconographia Diatomologica 26: [1] - 656."]}

Diploneis fossa sp. nov. (LM Figs 178–185, SEM Figs 186–192) Valves are weakly asymmetric, elliptical to linear–elliptical with parallel margins and bluntly round apices (Figs 178–188). The length of the valve is 47.5–64 μm and the width of the valve is 23–27 μm. The axial area is narrow, lanceolate, widening at the center to form a longitudinally elongate and weakly asymmetric central area (Figs 178, 187, 190), 4–5 μm wide. Externally, the canal is lanceolate and slightly expanded in the middle of the valve with three rows of cribrate (45 poroids), 8–10 in 10 μm. Externally, each areola opens into deep pits. The inter-areolar thickenings have fin-like crest silica ridges serrated with ca. 9–12 fine notched edges (Fig. 189). The fin-like ridges along the canal are slightly bent into semi-circular shape, positioned towards the striae whereas those of the striae are only slightly bent positioned towards the canal, changing opposite direction only at valve mantle (Figs 187, 192). Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Isanga Bay, at 768 m elevation; rock scrape, 20 m water depth, collected SCUBA diving, 8°39’10.7” S 31°11’34.8” E, A. Jordan, 8 th October 2021 (holotype designated here, circled specimen BM-108982! = Fig. 184, isotypes ANSP-GC17211!, CANA-129334!). Type material CANA-129329. Registration: http://phycobank.org/103708 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S2c). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660301). Etymology:— The specific epithet ‘ fossa ’ refers to the ditch-like formation of the fin-like crest ridges. Ecology and distribution:— This species has only been observed on the Zambian and Tanzanian coasts of Lake Tanganyika. In the alkaline, moderately mineral-rich and highly transparent waters, it inhabits sandy and muddy substrates (sometimes with mollusk shells) and submerged rocks between 5 and 33 m water depth. The largest population sizes of this species have been found in the southern parts of the lake in Isanga Bay and Mutondwe Island. Smaller population sizes were found in Chituta Bay, Kalambo Falls Lodge, Ndole Bay and in the central parts of the lake in Kalya Bay and Mahale National Park (Fig. 1c, e, f). In the type material, it mostly coexists with D. major sp. nov. while at all other sites it occurs with D. kilhamiana sp. nov., D. cocquytiana sp. nov., D. tumida sp. nov., D. cristata sp. nov., D. salzburgeri sp. nov., D. serrulata sp. nov., and D. duplex sp. nov. Main differential characters:— Valve shape, striae pattern, striae density, external fin-like ornamentations across the valve, fins scattered on the longitudinal canals, areolae formation over the longitudinal canal (thickened virgae), and poroids>45 per areola. Similar species:— Diploneis elongata sp. nov. and Diploneis raetica Lange-Bertalot & Fuhrmann (2020: 119)., Published as part of Jovanovska, Elena, Wilson, Mallory C., Hamilton, Paul B. & Stone, Jeffery, 2023, Morphological and molecular characterization of twenty-five new Diploneis species (Bacillariophyta) from Lake Tanganyika and its surrounding areas, pp. 1-102 in Phytotaxa 593 (1) on page 40, DOI: 10.11646/phytotaxa.593.1.1, http://zenodo.org/record/7875089, {"references":["Lange-Bertalot, H., Fuhrmann, A. & Werum, M. (2020) Freshwater Diploneis: species diversity in the Holarctic and spot checks from elsewhere. In: Lange-Bertalot, H. (Ed.) Diatoms of Europe. Diatoms of European inland water and comparable habitats. Freshwater Diploneis Two studies, Glashutten: Koeltz Botanical Books. pp. 1 - 526, 691 - 699."]}

Diploneis cristata sp. nov. (LM Figs 47–52, SEM Figs 53–60) Valves are weakly asymmetric, rhombic-elliptic to elliptic with convex margins and bluntly round apices (Figs 47–53). Valve length is 47–80.5 μm and valve width is 26–41 μm. The axial area is narrow, lanceolate, widening at the center to form a lanceolate central area (Figs 47, 55), 4.5–8.5 μm wide. Externally, the longitudinal canal is broad, lanceolate to linear, slightly expanded in the middle of the valve with three to four rows of cribrate (10–20 poroids) areolae narrowing into one at the valve apices (Figs 53, 55, 56). Internally, a thick non-porous slightly raised silica plate encloses the longitudinal canal (Figs 57, 59). Externally, the raphe is filiform, curved; the proximal ends are weakly deflected and positioned within a teardrop depression (Figs 53, 55). The distal raphe ends are unilaterally bent to the same side and terminate on the valve face (Figs 53, 56). Internally, the raphe branches are slightly arched with simple proximal and distal ends that are slightly elevated in a deep depression formed by the longitudinal canal (Fig. 57). The striae are parallel at mid-valve becoming radiate towards the valve apices, 7–8 in 10 μm. Striae are uniseriate throughout (Fig. 54). The striae are composed of large round to rectangular areolae covered externally with cribra (>40 poroids; hardly visible on the illustrated specimens), 7–8 in 10 μm. Each areola opens into deep pits and sometimes separated by short crested fin-like ridge ornamentations that are forming from the areolae wall (white arrowed Fig. 54). The inter-areolar thickenings have fin-like shaped silica ornamentations serrated into ca. 3–9 notched edges (Figs 54, 56). The areolae increase in size towards the valve margins (Figs 53, 55). Internally, the alveoli open via a single elongated opening covered with a thin silica layer (Figs 59, 60). The valvocopula has serrated advalvar edges (Figs 57, 59, 60). Type:— REPUBLIC OF ZAMBIA, Lake Tanganyika, Chituta Bay, at 768 m elevation; mud and mussels, 33 m water depth, collected SCUBA diving, 8°42’56.0” S 31°09’15.0” E, W. Salzburger, 5 th September 2018 (holotype designated here, circled specimen BM-108995! = Fig. 48, isotypes ANSP-GC17224!, CANA-129321!). Type material CANA-129321. Registration: http://phycobank.org/103701 Pictures of the isolated specimen:— LM micrograph on 1000× magnification (Fig. S2e). Sequence data:— Plastid gene rbc L sequence (GenBank accession: OQ 660279). Etymology:— The specific epithet ‘ cristata ’ is derived from the distinct crested fin-like ridge ornamentations on the valve face. Ecology and distribution:— Diploneis cristata sp. nov. has been observed along the Tanzanian and Zambian coasts of Lake Tanganyika. It is not a very frequent species in this alkaline lake with moderate mineral content, occurring mainly on muddy and sandy substrates between 5 and 25 m water depth, but also as tychoplankton in the littoral areas and in plankton up to 60 m depth. This species occurs mainly in the southern sub-basin at Kalambo Falls Lodge, Isanga Bay, Chituta Bay, Mutondwe Island, and Ndole Bay (Fig. 1c, f). In this sub-basin, the species occurs mainly together with D. gigantea sp. nov., D. fossa sp. nov., D. cocquytiana sp. nov., and D. salzburgeri sp. nov. Smaller population sizes of this species have been observed in the central and northern sub-basins in Kalya Bay, Mahale National Park, Rukoma area, Buhingu Island, and Kiganza Bay (Fig. 1c–e). In these areas, the species usually coexists with D. serrulata sp. nov., D. cocquytiana sp. nov., D. lunata sp. nov., D. salzburgeri sp. nov., and D. tanganyikae sp. nov. Main differential characters:— Valve size and shape, striae density, external thick fin-like ornamentations across the valve, fin-like thickening within areolae, and poroids>40 per areola. Similar species:— Diploneis tanganyikae sp. nov., D. salzburgeri sp. nov., and Diploneis buriatica Kulikovskiy & Lange-Bertalot (2015: 91)., Published as part of Jovanovska, Elena, Wilson, Mallory C., Hamilton, Paul B. & Stone, Jeffery, 2023, Morphological and molecular characterization of twenty-five new Diploneis species (Bacillariophyta) from Lake Tanganyika and its surrounding areas, pp. 1-102 in Phytotaxa 593 (1) on page 16, DOI: 10.11646/phytotaxa.593.1.1, http://zenodo.org/record/7875089, {"references":["Kulikovskiy, M. S., Lange-Bertalot, H. & Kuznetsova, I. V. (2015) Lake Baikal: hotspot of endemic diatoms II. Iconographia Diatomologica 26: [1] - 656."]}

Navicula sinicomeniscus Li & Metzeltin sp. nov. (LM: Figs 1–10, SEM: 11–16) LM: Valves linear-lanceolate, with cuneate ends and bluntly rounded apices (also the ends of largest specimens are never protracted). Length 55–75 µm, width 16–18 µm. Length/width ratio 3.3–4.1, median 3.7 (n=30). Raphe filiform, almost straight or weakly curved, and occasionally appears lateral. Central raphe ends expanded and inconspicuously deflected to the secondary side of the valve with drop-like central pores. Terminal raphe fissures rather small and bent towards the same side of the valve. Axial area moderately narrow, linear, slightly expanded proximally. Central area comparatively much less expanded, transversally widened, asymmetrical, shape variable, with one or few obviously irregularly shortened central striae. Striae radiate more strongly towards the center, subapical striae almost parallel, density 7–8 in 10 µm. Voigt faults appear indistinct. Areolae coarse and visible, 22–24 in 10 µm. SEM: External views: Raphe almost straight to slightly undulate with central raphe ends dilated, drop-shaped and slightly inclined to the secondary valve side. The terminal fissures clearly hooked in the same direction. Raphe sternum prominently developed, narrow, raised along the raphe, more obviously towards the center (arrow A in Fig. 11). Areolae slit-like (Figs 12, 13), with one row of apical areolae, arranged horizontally, positioned on the valve apex and mantle (arrow B in Fig. 12). Striae uniseriate, with two obviously shortened striae near the central area (arrows C in Fig. 13) and two occasionally intermittent striae (arrows D in Fig. 13). Internal views: Striae uniseriate, irregularly shortened in central area, composed of round-elliptical, roundrectangular areolae, separated by robust silica ribs. Sternum broad and raised, not interrupted, scarcely expanded in the central pore and inclined to the secondary valve side; lacking central area besides the sternum (black arrows in Figs 14, 16). Raphe continuous, lacking an intermissio. Terminal raphe ends terminate in small and knob-like helictoglossae (Fig. 15). Type: CHINA. Yunnan Province: Fuxian Lake, Fuxian 46–1, 24°24.870′ N, 102°50.590′ E, elevation 1720 m asl, Prof. Yan-Ling Li, 28th March 2005 (holotype Praep. Fuxian 46– 1 in Coll. Yan-Ling Li, Yunnan University, Kunming, China = Fig. 4). Etymology: the epithet refers to the most similar established taxon and the country (China) of the type location. Ecology: Navicula sinicomeniscus was found in a low altitude freshwater lake with moderately alkaline pH (8.71) and very low concentrations of nutrients (TN 0.14 mg ̛L- 1, TP 0.02 mg ̛L- 1). The dominant diatom species discovered in this area include Aulacoseira granulata (Ehrenberg) Simonsen (1979: 58) (1.7 %), Cyclotella rhomboideo-elliptica Skuja (1937: 49) (6.9 %), Cyclotella krammeri Håkansson (1990: 263) (46.4 %), Fragilaria crotonensis Kitton (1869: 110) (7.8 %), Stephanodiscus minutulus (Kützing) Cleve & Möller (1882: 300) (1.1 %), Stephanodiscus hantzschii Grunow (in Cleve & Grunow 1880: 121) (8.6 %), and some unidentified species of Achnanthidium Kützing (1844: 152) (6.7 %) and an Amphora Ehrenberg ex Kützing (Kützing 1844: 107) sp. (4.3 %). These entities comprise more than 83 % of all diatoms enumerated in the samples., Published as part of Xiao, Qiao-Zhi, Guo, Ji-Shu, Tang, Zheng-Bin, Kociolek, John Patrick & Li, Yan-Ling, 2023, Navicula sinicomeniscus sp. nov. (Bacillariophyta; Naviculaceae), a new species from southwestern China, pp. 241-252 in Phytotaxa 591 (4) on page 243, DOI: 10.11646/phytotaxa.591.4.1, http://zenodo.org/record/7835506, {"references":["Simonsen, R. (1979) The diatom system: ideas on phylogeny. Bacillaria 2: 9 - 71.","Skuja, H. (1937) Algae. In: Handel-Mazzetti, H. (Ed.) Symbolae Sinicae - Botanische Ergebnisse der Expedition der Akademie der Wissenschaften in Wien nach Sudwest-China 1914 / 1918. J. Springer, Wien, pp. 1 - 106.","Hakansson, H. (1990) A comparison of Cyclotella krammeri sp. nov. and C. schumannii Hakansson stat. nov. with similar species. Diatom Research 5 (2): 261 - 271. https: // doi. org / 10.1080 / 0269249 X. 1990.9705118","Kitton, F. (1869) Notes on New York diatoms with description of a new species Fragilaria crotonensis. Hardwicke's Science-Gossip 5: 109 - 110.","Cleve, P. T. & Moller, J. D. (1882) Diatoms. Part VI. Esatas Edquists Boktryckeri, Upsala. pp. 277 - 324.","Cleve, P. T. & Grunow, A. (1880) Beitrage zur Kenntniss der Arktischen Diatomeen. Kongliga Svenska-Vetenskaps Akademiens Handlingar 17 (2): 1 - 121."]}

Chamaepinnularia taihangensis N.N. Cui & Q. Liu sp. nov. Figs 2–20 LM (Figs 2–11):— Large specimens, linear-lanceolate valves with capitate apices and margins with distinct triple curvatures (Figs 2–8). Small specimens, valves elliptic-lanceolate with capitate apices and with or without distinct triple curvature (Figs 9–11). Length 10–14 μm, width 3.0–3.5 μm. Axial area narrow, rhombic, widening toward the middle of valve and nearly reaching the valve margins. Central area rhombic. Striae slightly radiate in the central area and convergent toward the ends, 20–21 in 10 μm. Raphe straight, proximal raphe ends expanded and bent slightly to the same side, the terminal raphe fissures deflected to the same direction. SEM (Figs 12–20):— Externally, striae composed of elongated chamber-like areolae and covered by vela (Figs 12–16). Raphe straight and filiform. Proximal raphe ends expanded and unilaterally deflected (Figs 12, 14). Terminal raphe curved to hook-shaped and continuing onto the mantle (Figs 12, 13, 16). Axial area narrow, rhombic. Fascias present, forming rhombic central areas (Fig. 12). Internally, areolae openings interrupted by siliceous bridge that divides striae in two parts (Fig. 17), one small, rounded and located on the valve face-mantle junction, whereas the other elongated and located on the valve face. Proximal raphe ends unilaterally hooked (Fig. 19). Terminal raphe ends weakly deflected and terminated as well-developed helictoglossae (Figs 18, 20). Type:— CHINA. Taihang Valley, Shanxi Province, epiphyton, 35°12’ N, 113°20’ E, 1760 m asl., June 2020 (holotype SXU! slide THS202006086 = Fig. 3, Freshwater Algal Herbarium of Shanxi University, Taiyuan, China; isotype: COLO slide, J.P. Kociolek Collection). Etymology:— Named for the region in which it was found. Ecology and distribution:— C. taihangensis sp. nov. was found in Eight spring gorge, Taihang Valley. Conditions in the type material were as follows: Temperature 17.2 ºC, pH = 8.32, EC = 318.6 µs̽ cm-1, AT = 679.4 mm Hg, dissolved oxygen = 9.57 mg ̽L- 1 and total dissolved solids = 279.50 mg ̽L- 1. Associated diatom species: — The type population of C. taihangensis sp. nov. was found in samples associated with other species. In THS202006086, two dominant species were Achnanthidium minutissimum (Kützing) Czarnecki (1994: 157) (25.8 %) and Delicata sinensis Krammer & Metzeltin (2003: 121) (Krammer 2003) (24.0 %). Diatoma moniliformis (Kützing) D.M. Williams (2012: 260) represented 7.5 % of the community with Cymbopleura kuelbsii (Krammer 2003: 94) (5.8 %), Achnanthidium rivulare Potapova & Ponader (2004: 36) (4.0 %), Achnanthidium pyrenaicum (Hustedt) H.Kobayasi (1997: 148) (3.8 %), Denticula elegans Kützing (1844: 44) (3.0 %), Navicula antonii Lange-Bertalot (2000: 155) (Rumrich, U., Lange-Bertalot, H. & Rumrich, M. 2000) (2.8 %), and Chamaepinnularia taihangensis sp. nov. (2.0 %)., Published as part of Cui, Nini, Liu, Qi, Liu, Xudong, Nan, Fangru, Kociolek, John Patrick & Xie, Shulian, 2023, Chamaepinnularia taihangensis sp. nov. (Bacillariophyceae), a new diatom species from Taihang Valley, Shanxi province, China, pp. 184-192 in Phytotaxa 587 (2) on pages 185-186, DOI: 10.11646/phytotaxa.587.2.7, http://zenodo.org/record/7731953, {"references":["Czarnecki, D. B. (1994) The freshwater diatoms culture collection at Loras College, Dubuque, Iowa. Memoirs of the California Academy of Sciences 17: 155 - 174.","Krammer, K. (2003) Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. In: Diatoms of Europe, Diatoms of the European Inland waters and comparable habitats. Vol. 4. pp. 1 - 529.","Williams, D. M. (2012) Diatoma moniliforme: Commentary, relationships and an appropriate name. Nova Hedwigia Beiheft 141: 255 - 261.","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","Kutzing, F. T. (1844) Die Kieselschaligen Bacillarien oder Diatomeen. Nordhausen: zu finden bei W. Kohne, 152 pp. https: // doi. org / 10.5962 / bhl. title. 64360"]}

Brachysira heteropolaris Van de Vijver sp. nov. (Figs 1 –26 LM) Valves heteropolar, clavate. Valve outline lanceolate with convex margins. Apices not protracted, acutely rounded. At footpole slightly more elongated than at headpole. Valve dimensions (n=40): length 18–35 µm, width 6–8 µm, largest width above the valve middle. Axial area very narrow, linear. Two longitudinal ridges bordering the axial area, running from valve apices to central area. Central area usually small, rounded to elliptical, and raised. Occasionally valves with slightly larger central areas observed (see for instance Figs 7, 11). Raphe filiform, raphe branches straight with indistinct, simple central raphe endings. Striae radiate throughout the entire valve length, well discernible in LM, 28–30 in 10 µm. Irregular, short ridges present crossing the striae (e.g. Figs 1, 4, 8 & 14). Type:— UNITED KINGDOM. Loch Canmor 2 (=Loch Kinord), Aberdeenshire 2, Scotland, prep. Weissflog, slide IX-18-A 8 in BR! (holotype slide BR-4777 = Fig. 5). Registration: —http://phycobank.org/103608 Etymology:—The specific epithet “ heteropolaris ” refers to the heteropolar valve outline. Ecology & associated diatom flora:—The Weissflog slide was prepared based on material from Loch Canmor. In the Van Heurck collection in BR (Belgium), several slides from Loch Canmor are conserved, two of them labelled “Loch Canmor 2 – Aberdeenshire – Schottland ” (slides IX-18-A8 &A10). Loch Canmor, nowadays called Loch Kinord is a small, freshwater lake at Muir of Dinnet (Aberdeenshire, Scotland), a few kilometers east of the village of Ballater. This shallow (max. 2m depth) freshwater loch is a part of the Muir of Dinnet National Nature Reserve and an important resting place for wintering birds. The loch is characterised as being oligotrophic and low-alkaline (Bennion et al. 2004, Lang et al. 2012). The diatom flora in the slide is characterised by a high biodiversity. Dominant species include Brachysira follis, B. brebissonii, B. confusa, Encyonema neogracile Krammer (1997a: 177), Encyonopsis cesatii var. geitleri Krammer (1997b: 154), Frustulia saxonica Rabenhorst (1853: 50), Gomphonema coronatum Ehrenberg (1840: 211), G. lagerheimii A. Cleve (1895: 22), Tabellaria fenestrata (Lyngbye 1819: 180) Kützing (1844: 127), and several Eunotia and Pinnularia species. This species composition reflects dystrophic to oligo-trophic, circumneutral to acidic, oligosaprobic conditions (Lange-Bertalot & Moser 1994, Lange-Bertalot et al. 2017). Although most species in the slide are acidophilous, several species preferring calcium-carbonate enriched conditions such as Brachysira styriaca, Eucocconeis flexella (Kützing 1844: 80) F. Meister (1912: 95), and Navicula radiosa Kützing (1844: 91) are present, though in low abundances. Some of these, such as N. radiosa, could, however, also survive in low-alkaline conditions, though not in high abundances (Lange-Bertalot 2001)., Published as part of Vijver, Bart Van De, 2023, Brachysira heteropolaris, a new diatom (Brachysiraceae, Bacillariophyta) species observed in an historic Weissflog slide from Scotland (UK), pp. 47-52 in Phytotaxa 587 (1) on pages 48-49, DOI: 10.11646/phytotaxa.587.1.6, http://zenodo.org/record/7710708, {"references":["Bennion, H., Fluin, J. & Simpson, G. L. (2004) Assessing eutrophication and reference conditions for Scottish freshwater lochs using subfossil diatoms. Journal of Applied Ecology 41: 124 - 138. https: // doi. org / 10.1111 / j. 1365 - 2664.2004.00874. x","Lang, P., Krokowski, J., Ross, N. & Doughty, R. (2012) The rare green alga Pediastrum privum (Chlorophyta, Sphaeropleales) in a Scottish kettle loch: new to British freshwaters. The Glasgow Naturalist 25: 139 - 142.","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. (1997 b) Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 2. Encyonema Part., Encyonopsis und Cymbellopsis. Bibliotheca Diatomologica 37: 1 - 469.","Rabenhorst, L. (1853) Die Susswasser-Diatomaceen (Bacillarien.): fur Freunde der Mikroskopie. pp. 1 - 72. https: // doi. org / 10.5962 / bhl. title. 8348","Ehrenberg, C. G. (1840) Characteristik von 274 neuenArten von Infusorien. Bericht uber die zur Bekanntmachung geeigneten Verhandlungen der Koniglich-Preussischen Akademie der Wissenschaften zu Berlin 1840: 197 - 219.","Cleve, A. (1895) On recent freshwater diatoms from Lule Lappmark in Sweden. Bihang till Kongliga Svenska Vetenskaps-Akademiens Handlingar 21 (Afh. III, 2): 1 - 44.","Lyngbye, H. C. (1819) Tentamen hydrophytologiae danicae continens omnia hydrophyta cryptogama Daniae, Holsatiae, Faeroae, Islandiae, Groenlandiae hucusque cognita, systematice disposita, descripta et iconibus illustrata, adjectis simul speciebus norvegicis. pp. [i] - xxxii, [1] - 248, 70 pls. Hafniae [Copenhagen]: typis Schultzianis, in commissis Librariae Gyldendaliae. https: // doi. org / 10.5962 / bhl. title. 6079","Kutzing, F. T. (1844) Die Kieselschaligen Bacillarien oder Diatomeen. Nordhausen. pp. 1 - 152. https: // doi. org / 10.5962 / bhl. title. 64360","Lange-Bertalot, H. & Moser, G. (1994) Brachysira. Monographie der Gattung und Naviculadicta nov. gen. Bibliotheca Diatomologica 29: 1 - 212.","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. Schmitten-Oberreifenberg: Koeltz Botanical Books; p. 1 - 942.","Meister, F. (1912) Die Kieselalgen der Schweiz. Beitrage zur Kryptogamenflora der Schweiz. Materiaux pour la flore cryptogamique suisse. Vol. IV, fasc. 1. pp. [i] - vi, [1] - 254.","Lange-Bertalot, H. (2001) Navicula sensu stricto. 10 Genera separated from Navicula sensu lato. Frustulia. Diatoms of Europe 2: 1 - 526."]}

We present light and scanning electron microscopical observations on two new species of Navicula Bory sensu stricto from Southeast Asia. Navicula winoniformis Chudaev, Glushchenko, Kulikovskiy & Kociolek, sp. nov. differs from taxa with similar outline and size by the combination of simple drop-like external raphe endings deflected to the primary valve side, presence of well-developed external longitudinal grooves and relatively low lineolae density. Navicula sparsilineolata Chudaev, Glushchenko, Kulikovskiy & Kociolek, sp. nov. can be discriminated from the taxa of similar valve shape and size by consistently lower lineolae density, and from the majority of them also by the structure of external proximal raphe endings with small projections in proximal parts and larger triangular insertions in distal parts. Some remarks on Navicula species diversity and its distribution in the Southeast Asia are given.

During the analysis of an historic slide of Loch Canmor, Aberdeenshire (Scotland, UK) prepared by Eugene Weissflog and conserved in the Van Heurck collection (BR, Belgium), an unknown, heteropolar Brachysira taxon was observed that could not be identified using the currently available literature. The new species, described as Brachysira heteropolaris sp. nov., is characterised in having a strictly heteropolar, broadly lanceolate valve outline with non-protracted, acutely rounded apices. The new species was observed in a dystrophic-oligotrophic, weakly acidic lake, based on the analysis of the composing diatom flora, dominated by several Brachysira species, Gomphonema coronatum and Encyonopsis cesatii var. geitleri.

In this study, samples were collected from the Java Sea coasts, from the South China Sea in Hainan Island coasts and Quảng Yên region and Rú Chá mangrove near Hue in Central Vietnam. In studied samples a total of eight Luticola species have been observed. Three of the taxa studied are described herein as species new to science – Luticola orientalis sp. nov., L. cribriareolata sp. nov. and L. halongiana sp. nov. Under light microscopy (LM) L. orientalis sp. nov. and L. cribriareolata sp. nov. are similar with rhombic-lanceolate to rhombic/ elliptic-lanceolate to elliptic valve shapes and narrowly rounded apices. Both species can be easily distinguished by stria density (higher density in L. orientalis). Under SEM L. cribriareolata is characterized by cribrate areola occlusions, a character thus far observed only in three established species. The remaining species of the whole genus known thus far are characterized by hymenate areola. Similar morphology Luticola species have been observed from tropical mangrove forests from Madagascar but they all can be easily distinguished based on the lack of grooves in the central area. The third species – L. halongiana sp. nov. has rhombic-elliptic to rhombic-lanceolate valves with broadly rounded to slightly protracted apices in larger specimens. This species has a relatively broad central area. Also unique among brackish-water Luticola is the small, rounded stigma positioned almost midway between the valve center and valve margin. In the habitats from which the new species are described we also identified five established Luticola taxa including, L. belawanensis, L. celebesica, L. inserata, L. seposita and L. tropica. For those species we provide detailed SEM characteristics of valve ultrastructure, as well as the range of environmental conditions and geographic distribution within the study area.

Sellaphora tanghongquii Y.-L. Li sp. nov. (Figs 2–26) Description:— LM (Figs 2–20): Valves broadly linear, margins weakly undulate, slightly constricted near the middle, with round ends. Length 24.5–45.5 μm, width 9.0–11.0 μm, length/width ratio varying between 2.7–4.1, median 3.3 (n = 30). Raphe filiform, lateral and undulate towards the distal and proximal ends. The terminal raphe ends slightly hooked and deflected to the same side. The central raphe ends relatively straight and tipped with slightly inflated pores. Axial area narrow and undulate following the raphe. Central area oval or elliptical, occupying 1/5–1/3 the valve width. Striae radiate more strongly towards the poles, sparser and shorter around the valve center, density 14–17 in 10 µm in the middle portion, up to 22 in 10 µm towards the ends. In some specimens, a longitudinal ridge adjacent to the trough can be seen (see arrow in Figs 3–4). Areolae not visible. SEM: Valves external (Figs 21–23): Raphe undulate with central raphe ends slightly dilated with drop-shaped pores and slightly deflected towards the same side (Figs 21, 23), terminal fissures hooked, deflected towards the opposite side of the valve, terminating onto the mantle (Figs 21, 22). The axial area has shallow troughs on both sides, extending to the apical area and becoming progressively shallower (arrow A in Fig. 21), slightly expanded at the apical area (Figs 21, 22), with wavy edges near the middle region (Fig. 23). Striae uniseriate, slightly radiate throughout, and extending onto the mantle (Figs 21–23). Areolae are mostly square and elliptical, partly round, oval, or irregularly shaped along the axial area and central area. Compared with the areolae from the longitudinal ridge to the edge of the mantle (type I: 47–55 in 10 µm), the areolae from the longitudinal ridge to the trough (type II: 42–46 in 10 µm) are smaller (arrow B in Fig. 21). Each areola has almost 2–4 small holes internally (Figs 21–23). A row of separated and small pores is present along with the mantle (arrow C in Fig. 21). Polar bars are absent. Valves internal (Figs 24–26): Axial area straight and slightly expanded near the central area. Internal raphe straight, discontinuous with intermission. Central raphe ends not expanded, bending towards the same direction (Figs 24, 26). Terminal raphe ends offset, terminating in elongated and straight helictoglossae (Figs 24, 25). The apical area of the valve has a pore-like pit, and the striae in the apical area are covered by hymenate occlusions (Fig. 25). Striae are biseriate, slightly radiate, formed by round, elliptical, C-shaped, or irregularly shaped areolae (107–150 in 10 µm) delimited by slightly oblique orientated vimines (Figs 24–26). Type:— CHINA. Guangxi Zhuang Autonomous Region: the Gui River, GR 17, elevation 78 m asl., 24°15′33′′ N, 110°45′51′′ E, Dr. Hong-Qu Tang, 29th July 2021 (Holotype GR202172902! in Coll. Hong-Qu Tang, Jinan University, Guangzhou, China = Fig. 2). Etymology:— tanghongquii, honors Dr. Hong-Qu Tang, the collector of the type sample., Published as part of Ni, Hong-Ping, Guo, Ji-Shu, Tang, Zheng-Bin, Huang, Ying-Yan, Kociolek, John Patrick & Li, Yan-Ling, 2022, Sellaphora tanghongquii sp. nov. (Bacillariophyta, Sellaphoraceae), a new diatom species from the Southern China, pp. 103-114 in Phytotaxa 573 (1) on pages 106-108, DOI: 10.11646/phytotaxa.573.1.6, http://zenodo.org/record/7329529

Craspedostauros confusus Zidarova, M.de Haan, P.Ivanov, Hineva & Van de Vijver sp. nov. (Figs 9– 6, 8, 8–56) Description LM observations (Figs 9– 6, 8):— Frustules lanceolate in girdle view with convex, rarely weakly constricted (and hence biarcuate) margins, bearing numerous copulae. Longer valves linear with broadly rounded apices (Fig. 19), becoming narrowly lanceolate to elliptic-lanceolate in smaller valves with more cuneately rounded (Figs 21, 22), sometimes almost subrostrate apices (Fig. 23). Valve margins weakly convex (Fig. 21) to almost straight in the middle (Figs 20, 22, 24), lacking any constriction. Valve dimensions (n = 16): length 22.0–49.5 µm, width 4.5–6.5 µm. [Valves (n = 27) observed in other populations on Livingston Island during the study (Figs 60–77, 79) had a valve length of 18–50 µm and a valve width of 4.0–6.5 µm]. Axial area very narrow, linear (Figs 19–24, 28). Central area narrow, forming an almost rectangular (Fig. 19) to bow-tie-shaped fascia (Figs 20–24, 28), widening towards the valve margins. Raphe filiform, straight (Fig. 19) to weakly undulating, with expanded central raphe endings, and elongated terminal raphe fissures, unilaterally weakly bent (Figs 21, 24, 28). Striae rather coarse, parallel to occasionally very weakly radiate in the middle (Fig. 22), parallel to very weakly convergent near the apices (Figs 19, 24), 22–24 in 10 µm. Areolae, at least the larger ones bordering the axial area, weakly discernible in LM (Fig. 19). SEM observations (Figs 8–56):— Valve face weakly domed, with a deep mantle (Figs 48–51). External raphe branches straight with weakly undulating (Fig. 49) to straight (Fig. 51) central raphe endings, terminating in drop-like expanded pores (Figs 49, 51). Terminal raphe fissures continuing shortly onto the mantle, unilaterally hooked (Figs 48, 51). Axial area triangularly expanded at the apices, bearing a silica flap on one side, covering the terminal raphe fissures (Fig. 50). Striae uniseriate, composed of cribrate, rounded to elliptic areolae. Near the raphe areolae clearly larger (Figs 49, 50 and Figs 88–90). Cribrum structure of the areolae bordering the axial area possessing four to seven peripheral pores, and two to three central pores. All other areolae with cribra composed of 2–5 peripheral pores, lacking central pores (Figs 49, 50). Areolae continuing around the apices (Figs 48, 50), ca. 25–30 in 10 µm. Internal areolar openings rounded to elliptic (Figs 53–56). Internal raphe straight, located on a distinct sternum (Figs 52, 53). Central raphe endings terminating onto double helictoglossae (Figs 53, 55). Terminal raphe endings finish onto broad helictoglossae. Stauros narrow, located on a wider hyaline fascia (Figs 52, 53, 55). Type:— ANTARCTICA. South Shetland Islands: Livingston Island, Hannah Point, sample 14 (62° 39’13” S, 60° 36’ 41” W), marine epilithon, R. Zidarova, 16th December 2018 (holotype BR-4760! = Fig. 28, isotype Slide 417! (University of Antwerp, Belgium)). Etymology:— The species epithet, confusus, Latin for confusing, reflects the complex taxonomic history of the genus Craspedostauros in the Antarctic Region, and the possible long-term inclusion of this species within the more common Antarctic species C. laevissimus. Ecology and associated diatom flora:— Craspedostauros confusus sp. nov. was found as abundant in the epilithon of several tidal pools at Hannah Point (sample 14, type), Mongolian (Reserve) Port (samples DNA5 and MO’), and Caleta Argentina (sample LT6). The salinity level in the pools (when measured) ranged between 33 and 35 PSU (Table 1), and their diatom flora was dominated by various species, including Navicula spp., Melosira spp., Parlibellus sp., Tabulariopsis australis (Peragallo 1921: 67) D.M. Williams (1988: 249) and Tripterion margaritae (Frenguelli & Orlando 1958: 98) L.F. Fernandes & Sar (2009: 67)., Published as part of Zidarova, Ralitsa, Haan, Myriam De, Ivanov, Plamen, Hineva, Elitsa & Vijver, Bart Van De, 2022, The genus Craspedostauros E. J. Cox (Bacillariophyta) on the coasts of Livingston Island, Maritime Antarctica, pp. 1-24 in Phytotaxa 572 (1) on page 12, DOI: 10.11646/phytotaxa.572.1.1, http://zenodo.org/record/7305672, {"references":["Peragallo, M. (1921) Diatomees d'eau douce et diatomees d'eau salee. In: Deuxieme Expedition Antarctique Francaise (1908 - 1910) commandee par le Dr. Jean Charcot. Sciences Naturelles, Documents Scientifiques, Botanique, Masson et Cie, pp. 96 + Pl. https: // doi. org / 10.5962 / bhl. title. 64272","Williams, D. M. (1988) Tabulariopsis, a new genus of marine araphid diatom, with notes on the taxonomy of Tabularia Williams et Round. Nova Hedwigia 47: 247 - 254.","Frenguelli, J. & Orlando, H. A. (1958) Diatomeas y silicoflagelados del sector Antartico Sudamericano. Instituto Antartico Argentino Publicacion No. 5: 1 - 191.","Fernandes, L. F. & Sar, E. A. (2009) Fine morphology of Gomphonema margaritae Frenguelli & Orlando and its validation and transfer to Tripterion Holmes, Nagasawa & Takano. Diatom Research 24: 63 - 78. https: // doi. org / 10.1080 / 0269249 X. 2009.9705783"]}

Craspedostauros laevissimus (West & G.S.West 9: 8) Sabbe (00: 5) (Figs – 8, 7, 9– 7, 80–85) LM observations (Figs – 8, 7, 80–85):— Frustules rectangular, lanceolate in girdle view with weakly convex margins (Figs 7, 8), constricted in the middle (i.e. biarcuate), with numerous copulae (Fig. 18). Longest valves linear (Figs 80, 83, 85), linear-lanceolate, smaller valves becoming elliptic-lanceolate (Figs 4, 13, 15, 27). Apices broadly rounded (Figs 4, 15, 27), to almost cuneate (Figs 2, 3, 13). Valve margins in the middle ranging from occasionally almost straight (Fig. 83) to, usually, weakly (Figs 3, 5) to moderately (Figs 4, 9) convex. Valve dimensions (n = 26): valve length 20–42 µm, valve width 4.5–7.0 µm. Occasionally, weakly silicified valves, probably in state of formation, and easily “squashed” on the slides, appear to have a larger valve width (see for instance Figs 81, 82, 84). Axial area very narrow, linear. Central area variable in size, from very narrow (Figs 9, 11), almost rectangular (Figs 3, 16) to bow-tie-shaped fascia, widening towards the margin (Figs 2, 4, 5, 27). Raphe filiform, slightly curved to straight, with enlarged central raphe endings, and elongated, unilaterally bent, terminal raphe fissures. Striae fine, parallel, occasionally very weakly radiate in the middle, 28–30(32) in 10 µm. Areolae not or occasionally slightly individually discernible in LM. SEM observations (Figs 9– 7, 86–87):— Externally, valve face curving into a deep mantle (Figs 29, 38). Raphe almost straight (Figs 29, 32, 36, 39) or sometimes weakly undulating (Fig. 35). Central raphe endings weakly curved and enlarged (Figs 29–30, 32–33, 35, 37), occasionally straight and only weakly expanded (Figs 39–40). At the apices, axial area triangularly widening, forming a silica flap (Figs 38, 41) on one side covering the terminal raphe fissures. Fissures continuing shortly onto the mantle (Figs 31, 34, 35, 38, 39, 41), clearly unilaterally bent (Figs 35, 36) to weakly hooked (Fig. 38). Striae uniseriate, composed of cribrate areolae of almost equal size (Figs 30, 35, 39, 40, 45) to slightly larger near the axial area (Figs 37, 40, 41). Larger areolae, apparently formed by merging two adjacent areolae occasionally present near the axial area (Figs 31, 87, arrows). Areolae continuing around the apices (Figs 31, 34, 38). Cribra composed of usually four (Figs 34, 37, 40, 42), rarely five (Figs 33, 34, 40) peripheral pores, although very rarely, up to 6–7 very small peripheral pores were observed (Fig. 41), or very occasionally only 1–3 (Fig. 45). In general, areolae near the axial area more complex, with more peripheral pores, whereas areolae on the rest of the valve face simplified having a lower number of peripheral pores (Figs 40, 45). Central cribrum pores usually single or absent (Figs 30, 37, 40), occasionally 2–3 (Figs 31, 33, 34, 41). Areolae uniformly distributed over the valve face, ca. 40 in 10 µm. Internally, areolar openings square to rectangular (Figs 46, 47), to almost rounded (Figs 43, 45). Internal raphe branches straight, located on a distinctly raised sternum. Central raphe endings terminating onto double helictoglossae (Figs 43, 45, 46). Stauros narrow, located on a wider hyaline fascia (Figs 43–46). Terminal raphe endings finish onto broad helictoglossae (Figs 46, 47). Ecology and associated diatom flora:— The species was often found in the epilithon of tidal pools at Hannah Point (samples 11 and 13, and LT10), having variable salinity levels between 11.5 and 33.7 (Table 2), but it was most abundant in sample 13. The diatom flora of this sample included Melosira spp. and several unidentified Navicula taxa in larger numbers., Published as part of Zidarova, Ralitsa, Haan, Myriam De, Ivanov, Plamen, Hineva, Elitsa & Vijver, Bart Van De, 2022, The genus Craspedostauros E. J. Cox (Bacillariophyta) on the coasts of Livingston Island, Maritime Antarctica, pp. 1-24 in Phytotaxa 572 (1) on pages 4-7, DOI: 10.11646/phytotaxa.572.1.1, http://zenodo.org/record/7305672

Placoneis asymmetricus Glushchenko, Kezlya, Kulikovskiy & Kociolek, sp. nov. (Figs 2-4) HOLOTYPE. — Vietnam. Đồng Nai Province, Cát Tiên National Park, from soil sampled at Đồng Nai riverside, 11°26’05.6”N, 107°25’44.8”E, 03.VI.2019, E.S. Gusev & E.M. Kezlya, slide no. 06728 (oxidized material of cultured strain VP57). Deposited in the collection of Maxim Kulikovskiy at the Herbarium of the Institute of Plant Physiology, Russian Academy of Science, Moscow, Russia (Fig. 2P). ISOTYPE. — Same data as holotype, slide no. 06728a. Deposited in the collection of the Main Botanical Garden of the Russian Academy of Science, Moscow, Russia (MHA). TYPE LOCALITY. — Vietnam. Đồng Nai Province, Cát Tiên National Park, Đồng Nai riverside, 11°26’05.6”N, 107°25’44.8”E. ETYMOLOGY. — The specific epithet refers to the typical asymmetry of the valves of this species. SEQUENCE DATA. — Nuclear-encoded SSU rDNA partial sequence (GenBank accession: MW 979509), plastid gene rbc L partial sequence (GenBank accession: MW 987572). DISTRIBUTION. — So far only known from the type locality. DESCRIPTION LM (Fig. 2) Cells solitary, rectangular in girdle view, with a single chloroplast with medially positioned centre and lobes beneath both valves (Fig. 2 A-I). Chloroplasts share the characteristic organization typical for the genus (Mereschkowsky 1903; Cox 1987, 2003). The chloroplast is single, large, and extends along the inner surface of the cell. The central column (isthmus) is offset to one side from the central axis and forms a slight bend. Libroplast is missing or represented by only one granule (Fig. 2A, F). The chloroplast has four irregular outgrowths (similar to petals) extending from the isthmus. Valve are linear-elliptical, slightly asymmetric along the longitudinal axis (Fig. 2 J-Z). Apices are bluntly rostrate, often asymmetric, breadth 1.3-2.0 µm. Valve length 10.3- 15.4 µm, valve width 6.0-6.8 µm. Axial area narrow, almost linear, very slightly wided towards the valve middle. Central area is absent. Raphe filiform, straight, central pores are small. The structure of distal raphe ends not discernible in the LM. Striae radiate, 17-21 in 10 µm, in the valve middle 2-3 irregularly shortened striae are present on each side. Areolae not resolvable in LM. SEM external views (Fig. 3) Valve face is flat. Raphe narrow, linear (Fig. 3A). Proximal raphe ends straight, small, slightly expanded (Fig. 3B). Distal raphe ends hook-shaped, extending to the valve mantle and unilaterally bent (Fig. 3A, C). Striae composed of 3-11 rounded or weakly elongated areolae, continuing onto the valve mantle. Areolae 45-50 in 10 µm. Stigma is absent. SEM internal views (Fig. 4) The raphe is straight (Fig. 4A). Proximal raphe ends are hooked-shaped and deflected to one side (Fig. 4B). Distal ends terminating on small helictoglossae and may be slightly deflected to opposite sides (Fig. 4A, C). The striae are bordered by broad interstriae (virgae) (Fig. 4C). Areolae small, square or round.Two isolated areolae are present at the apices (Fig. 4C). Volate occlusions were not preserved during the material treatment., Published as part of Kezlya, Elena, Glushchenko, Anton, Kociolek, John Patrick, Maltsev, Yevhen, Genkal, Sergey & Kulikovskiy, Maxim, 2022, A new species of Placoneis Mereschkowsky (Bacillariophyceae: Cymbellales) from wet soils in southern Vietnam, pp. 177-188 in Cryptogamie, Algologie 20 (11) on pages 180-181, DOI: 10.5252/cryptogamie-algologie2022v43a11, http://zenodo.org/record/7829344, {"references":["MERESCHKOWSKY C. 1903. - Uber Placoneis, ein neues Diatomeen- Genus. Beihefte zum Botanischen Centralblatt 15 (1): 1 - 30.","COX E. J. 1987. - Placoneis Mereschkowsky: the re-evaluation of a diatom genus originally characterized by its chloroplast type. Diatom Research 2 (2): 145 - 157. https: // doi. org / 10.1080 / 0269 249 X. 1987.9704994","COX E. J. 2003. - Placoneis Mereschkowsky revisited: resolution of several typification and nomenclatural problems, including the generitype. Botanical Journal of the Linnean Society 141 (1): 53 - 83. https: // doi. org / 10.1046 / j. 1095 - 8339.2003.00115. x"]}

Kezlya, Elena, Glushchenko, Anton, Kociolek, John Patrick, Maltsev, Yevhen, Genkal, Sergey, Kulikovskiy, Maxim (2022): A new species of Placoneis Mereschkowsky (Bacillariophyceae: Cymbellales) from wet soils in southern Vietnam. Cryptogamie, Algologie 20 (11): 177-188, DOI: 10.5252/cryptogamie-algologie2022v43a11, URL: http://dx.doi.org/10.5252/cryptogamie-algologie2022v43a11

Diploneis guangdongensis W.W.Wu, Y.H.Gao & C.P.Chen spec. nov. (LM Figs 1–20, SEM Figs 21–32) Description:— LM: The valves are elongated-elliptical with parallel margins and round apices (Figs 1–20). The valve length is 6.5–12 µm, and the breadth is 3.0–4.0 µm. The axial area is narrow. The central area is distinct and quadratic to slightly rectangular in shape. Longitudinal canals are narrow and lanceolate in the flat median portion. The raphe is a narrow straight slit. Striae are not visible under LM. SEM: The valve surface is almost flat. Along both sides of the axial area, the longitudinal canal is lanceolate and linear, open outside by one row of C-shaped poroids throughout the whole length of the valve (Figs 22–24). The openings of the canal are covered with volate occlusions externally (Figs 23, 26). At the valve apices, the longitudinal canal circles the distal raphe endings (Figs 21–23). The axial area is very narrow and linear. The central area is quadratic to slightly rectangular, ca. 0.83–0.90 µm wide. Externally, the raphe is a narrow straight slit, with simple and slightly expanded drop-like proximal ends (Figs 24–25). The distal raphe ends are simple and bent to the same side of the valve, terminating at some distance from the valve apices (Figs 22–23). The area with volate occlusions occupies approximately one-fourth to one-sixth of the valve width (Figs 21, 26). The alveoli open externally via elongated slits (Fig. 22, white arrow). The slits are the areola occlusions, short and narrow, rarely branched. The striae are parallel in the middle of the valve, becoming slightly radiated at the valve apices, 30–35 in 10 µm. The elongated slits are formed as an interspace between costae with the same shape (Fig. 24, white arrow). Each marginal flap is elongated to the margin of the valve. The other part of the alveolate striae is covered by a broadly semilune hyaline area at the middle of the valve, merging with the longitudinal canal (Figs 21, 25). Internally, the longitudinal canal is nonporous and enclosed by a thick silica plate (Figs 27, 29–30). The internal longitudinal canal is less silicified, the raphe is not placed in a depression formed by the longitudinal canals. The proximal raphe ends are slightly expanded into small, drop-like central pores bent to the same side of the valve (Figs 29, 32). The distal raphe ends are slightly expanded and straight (Figs 30–31). Transapical costae are narrower than alveoli in both inner and outer valves (Figs 24–25, 27, 29). The intercostal spaces consist of elongated alveoli (Figs 29–30), each occluded by a thin siliceous layer, bearing perforations in a hexagonal array (Figs 29–30). The cingulum is composed of two copulae without ornamentation (Figs 25, 28). Type: — CHINA. Guangdong Province, Shantou City, sandy beach, 23.4378°N, 117.1369°E, 10 May 2020, L.Y. Tan, (holotype slide ST-200510-1! = Fig. 2; isotype Slide ST-200510-2, both deposited in the Biology Department Herbarium, Xiamen University (AU), China. Etymology: — The epithet “ guangdongensis ” refers to the site where the new taxon was collected., Published as part of Wu, Weiwei, Sun, Lin, Li, Xuesong, Liang, Junrong, Gao, Yahui & Chen, Changping, 2022, A new small marine Diploneis species (Diploneidaceae, Bacillariophyta) from Guangdong Province, China, pp. 233-240 in Phytotaxa 560 (2) on pages 234-235, DOI: 10.11646/phytotaxa.560.2.6, http://zenodo.org/record/7040545

A Diploneis species new to science is described here, collected from an intertidal sandy beach in Guangdong Province, China. The species has morphological features such as small elongated-elliptical valves, a linear longitudinal canal open outside by one row of C-shaped areolae throughout the whole length, a straight and simple raphe, alveoli occluded externally by a vola and internally by a thin hymen, perforations arranged in a hexagonal array that occupy approximately one-fourth to one-sixth of the valve width, and the other part of the alveolate striae covered by a broadly semilune hyaline area at the middle of the valve. Differences with other similar taxa of this genus are discussed.

Frustulia hengduanensis sp. nov. Fen Luo & Quanxi Wang (LM Figs 1–14, SEM Figs 15–24) Description:— LM: Valves elliptico-lanceolate or rhomboid with slightly undulate margins. Apices narrowly rounded and moderately protracted. Valve length 43–55 μm, breadth 11–14 μm (n=30). The longitudinal ribs slightly curved. On the valve face, the striation patterns are weakly discernible under LM. Striae absent within the central area, forming a dumbbell-shaped hyaline zone (Figs 1–14). SEM: External view, the striae parallel at the valve center and slightly convergent towards the apices, with 36–40 striae per 10 μm (Fig. 15). Striae wavy along the length of the valve (Figs 15–16). The valve ends circumradiated by one or two rows of areolae (Figs 18–19). Areolae rounded to elliptical at the valve center and more slit-like distally, with 33–36 areolae per 10 μm (Figs 17–18). Striae absent within the central area, forming a dumbbell-shaped hyaline zone (Figs 16–17). The raphe is filiform, and both the proximal and the terminal raphe ends are T-shaped (Figs 17–19). Internal view, areolae have circular to rectangular hymenes (Fig. 22). Both the longitudinal ribs and the raphe slightly curved (Fig. 20), while both proximal and terminal raphe ends are straight (Figs 21–24). At the apices, the longitudinal ribs and the helictoglossae fuse to form a small porte-crayon (Fig. 24). Type: — CHINA. Sichuan Province: Hengduan Mountains, Q.X. Wang, F. Luo and colleagues, August 2015 (holotype SHTU! SC201508131, Biology Department Diatom Herbarium, Shanghai Normal University, Shanghai, China = Fig. 2. Isotype YXNU! SC201508131, Biology Department Diatom Herbarium, Yuxi Normal University, Yuxi City, Yunnan Province, China). Etymology: —The species is named for its type locality in the Hengduan Mountains. Ecology: —All samples were collected from fen peat and a stream fen at elevations of 4160–4750 m asl in freshwater at 5.3–15.3 °C, with pH 6.9–8.1, salinity 0.01–0.08 ‰, and conductivity 20–91 μs∙ cm-1.. Distribution: —This species is known from five samples collected in the Haizi Mountain Reserve, Daocheng County, Sichuan Province, China (slide nos. SC201508127, SC201508128, SC201508131, SC201508132, and SC201508137) and from one sample collected in Zuogong County, Tibet (slide no. HDS201810304)., Published as part of Luo, Fen, You, Qingmin, Yu, Pan & Wang, Quanxi, 2022, Frustulia hengduanensis sp. nov. a new diatom (Bacillariophyceae) from Hengduan Mountains, China, pp. 193-199 in Phytotaxa 559 (2) on pages 195-196, DOI: 10.11646/phytotaxa.559.2.8, http://zenodo.org/record/7021627

We describe Frustulia hengduanensis sp. nov., a new species of Frustulia from the Hengduan Mountains in China, based on morphological examinations using light and scanning electron microscopy. Frustulia hengduanensis is characterized by elliptico-lanceolate to rhomboid valves with slightly undulate margins, narrowly rounded and moderately protracted apices, slightly curved longitudinal ribs and raphe, wavy striae along the length of the valve, and an absence of striae within the central part of the valve, forming a dumbbell-shaped hyaline area, this is the main feature that distinguishes the new species from others in the genus. We compared F. hengduanensis sp. nov. with similar taxa and discussed its biogeographical distribution.

Hippodonta mudumalaiensis A.Vigneshwaran & B.Karthick sp. nov. (Figs 2–39, Fig. 22 represents the holotype) Description:— LM (Figs 2–29): Cells solitary, valves narrow-lanceolate to rhombic-lanceolate with broadly rounded apices. Valve length 13.0–20.0 μm, width 5.0–6.2 μm (n=67). Axial area narrow-linear, tilted, slightly asymmetric to the apical axis. Central area broadened with short single striae, shorter striae present at any one side; Striae radiate near centre and parallel near apices; no fascia is formed. Raphe linear-filiform, weakly pronounced, small teardrop-shaped and closely spaced central endings. Distal ends of raphe discernible in LM, equally pronounced as central endings, teardrop-shaped. Raphe distal ends positioned before terminal area or weakly advancing into slightly curved towards valve side. Terminal area distinguishable in LM, narrow, lunate and cap-like. Striae coarse, evenly spaced throughout valve, weakly to moderately radiate in the middle, becoming parallel or weakly convergent towards ends, 10–12/10 μm. Lineolae not discernible in LM. SEM (Figs 30–39): Externally (Figs 30–34), valves with flat face and slightly convex central area (Figs 30–32). Axial area slightly asymmetric (Fig. 30). Proximal raphe endings strongly pronounced, teardrop-shaped and bent towards same side as distal ends (Figs 31, 32). Terminal pores of raphe distinct, advancing towards the terminal area and deflected towards one valve side (Figs 33, 34). Terminal septa clearly developed and bordered by semi circumpolar (Figs 33, 34). Slit-like elongated areolae positioned on apical valve mantle, 40–50 in 10 μm. Striae uniseriate throughout valve, simple apically elongated lineolate, 50–60/10 μm. Rarely near central area transapically elongated lineolate areolae (Fig. 32). Striae in the central area clearly shortened, one side longer than the other side (Figs 30, 32). Prominent hyaline area present throughout the valve mantle (Fig. 31). Internally (Figs 35–39), striae placed in shallow linear depressions. Areolae covered by hymens. Central raphe endings simple, linear and gradually disappear (Fig. 38). Small wedge-shaped hyaline area present at centre. Distal raphe endings terminate on small defused helictoglossae (Figs 35, 36, 39). Terminal area internally prominent and bordered by hymenated linear depressions (Fig. 39). Type:— INDIA. Masinagudi, Nilgiris, Tamil Nadu. Stream, 11°33’14.8” N, 76°37’21.6” E, altitude 940 m asl, was collected by Mr. Kannan Govindarajan. (holotype AHMA! Slide #1752 = Fig. 22). Type material AHMA #1752. Habitat:— Epilithic, submerged stones in the stream. Water chemistry measurements includes pH of 7.35, nitrate (low range, NO 3 –) 0.03 mg ∙L- 1; dissolved oxygen (DO) 6.84 mg ∙L- 1; conductivity: 635 μS∙ cm-1; water temperature: 23.6 °C, total dissolved solids (TDS) 276 mg ∙L- 1. Etymology:— The specific epithet “ mudumalaiensis ” refers to the name of the location from which this new taxon is identified., Published as part of Vigneshwaran, Anbukkarasu, Wadmare, Neha & Karthick, Balasubramanian, 2022, A new species of Hippodonta Lange-Bertalot, Metzeltin & Witkowski (Bacillariophyceae, Naviculales) from the Western Ghats, India, pp. 219-228 in Phytotaxa 558 (2) on pages 222-223, DOI: 10.11646/phytotaxa.558.2.5, http://zenodo.org/record/7002983

Vigneshwaran, Anbukkarasu, Wadmare, Neha, Karthick, Balasubramanian (2022): A new species of Hippodonta Lange-Bertalot, Metzeltin & Witkowski (Bacillariophyceae, Naviculales) from the Western Ghats, India. Phytotaxa 558 (2): 219-228, DOI: 10.11646/phytotaxa.558.2.5, URL: http://dx.doi.org/10.11646/phytotaxa.558.2.5

Stauroneis lacuspowaiensis Wadmare & B.Karthick nom. nov., stat. nov. (Figs 1–18, Fig. 4 represents the lectotype) Basionym: — Stauroneis phoenicenteron f. capitata in Gonzalves & Gandhi 1953, The Journal of Indian Botanical Societ y, p. 256, fig. 92 (here reproduced as Fig. 1) Heterotypic synonym: — Stauroneis nobilis f. capitata H.Kobayasi (in Kobayasi & Ando 1977) Type:— INDIA. Mumbai (then Bombay), Maharashtra. Powai Lake pavements having encrustations with dead vegetable matter, 19°7’37.2” N, 72°54’14.4” E, Mr. H. P. Gandhi on 6 th March 1945 . Lectotype (designated here):—Agharkar Research Institute (AHMA) Gandhi Collection! Slide- Sr 5, here illustrated as Fig. 4. Description:—LM (Figs 1–8): Valves narrowly linear-lanceolate, having large, capitate apices with slight undulate sides (Fig. 5, arrow). Length 98.5–103.0 µm, breadth 16.5–18.0 µm. Axial area broad widening near centre. Stauros slightly broad, rectangular. Raphe thick with straight central raphe ends, and sickle-shaped terminal raphe fissures with bifurcation (Fig. 7, arrowhead). Striae parallel at centre and radiate towards apices, 18–23/10 µm. Areolae irregularly punctate (Fig. 4, double arrowheads), discernible in LM. (n= 21). SEM (Figs 9–18): Externally (Figs 9–14), central raphe ends terminating on stauros (Figs 9, 10, 12). Raphe filiform (Fig. 12). Terminal raphe fissures sickle-shaped, continuing onto mantle (Figs 11, 13). Striae uniseriate, composed of irregularly placed, transapically elongated, slit-like areolae (Fig. 14, double arrowheads). Internally (Figs 15–18), stauros small, thickened and elevated with tunnel gap (Figs 15, 17, arrowheads). Terminal raphe fissures terminating onto helictoglossae (Figs 15, 16, 18). Areolae rounded to transapically elongated, 16–20 in 10 µm (Fig. 17, double arrowheads). Remarks:—Valve dimensions of the specimens examined in the current study have a smaller size range than the dimensions given by H. P. Gandhi in the original description length 113.4–120.0 µm; width 21.6 µm (see Table 1). In addition, previous studies based on Gandhi’s material observed certain morphometry discrepancies (Karthick & Kociolek 2012, Kale et al. 2017). Etymology:—The specific epithet “ lacuspowaiensis ” refers to the type locality Powai Lake, Mumbai, where H. P. Gandhi originally collected the sample., Published as part of Wadmare, Neha & Karthick, Balasubramanian, 2022, Revisiting two Stauroneis Ehrenberg (Bacillariophyta) from H. P. Gandhi's Diatom collection: Notes on Ultrastructure, Types and Nomenclature, pp. 42-52 in Phytotaxa 555 (1) on page 44, DOI: 10.11646/phytotaxa.555.1.3, http://zenodo.org/record/6875613, {"references":["Gonzalves, E. A. & Gandhi, H. P. (1953) A systematic account of the Diatoms of Bombay and Salsette - 11. Journal of the Indian Botanical Society 32: 239 - 263.","Kobayasi, H. & Ando, K. (1977) Diatoms from irrigation ponds in Musashikyuryo-shinrin Park, Saitama Prefecture. Bulletin of Tokyo Gakugei University 29: 231 - 263.","Karthick, B. & Kociolek, J. P. (2012) Reconsideration of the Gomphonema (Bacillariophyceae) species from Kolhapur, Northern Western Ghats, India: Taxonomy, typification and biogeography of the species reported by H. P. Gandhi. Phycological Research 60: 179 - 198. https: // doi. org / 10.1111 / j. 1440 - 1835.2012.00649. x","Kale, A., Levkov, Z. & Karthick, B. (2017) Typification of two species of Luticola (Bacillariophyta) from aerophilic habitats of the Western Ghats, India. Phytotaxa 298: 29 - 42. https: // doi. org / 10.11646 / phytotaxa. 298.1.3"]}

Stauroneis dharwarensis Wadmare & B.Karthick nom. nov., stat. nov. (Figs 19–41, Fig. 24 represents the lectotype) Basionym:— Stauroneis anceps f. indica in Gandhi 1959a, Ceylon Journal of Science (Biology Section), p. 104, 105, fig. 25 (here reproduced as Fig. 19). Type:— INDIA. Dharwar, Karnataka. Dharwar pools from paddy and millet fields watercourses during rains, 15°26’34.8” N, 74°54’43.2” E. Mr. H. P. Gandhi on 14 th August 1949 . Lectotype (designated here):—Agharkar Research Institute (AHMA) Gandhi Collection! Slide- Sr 48, here illustrated as Fig. 24. Description:—LM (Figs 19–31): Valves broadly lanceolate with constricted, subrostrate to rostrate apices. Length 32.0–64.0 µm, breadth 12.0–15.0 µm. Axial area narrow, widening at centre. Stauros bow-tie shaped, widening towards valve margin. Raphe slightly coarse with straight central raphe ends, terminal raphe fissures unilaterally deflected. Striae strongly radial punctate, 17–19/10 µm. Areolae punctate to transapically elongated, discernible in LM. (n= 36). SEM (Figs 32–41): Externally (Figs 32–36), valves linear-lanceolate with axial area narrow throughout but wider at centre (Figs 32, 36). Central raphe ends tear-drop shaped (Figs 32, 33). Terminal raphe fissures continuing onto mantle (Figs 34, 35). Striae uniseriate, composed of transapically elongated areolae, 24–28 in 10 µm (Figs 33–35). Internally (Figs 37–41), stauros broad, thickened and expanded (Figs 37, 38, 40). Central raphe ends slightly deflected, terminating onto well-developed stauros (Figs 38, 40). Terminal raphe fissures terminating onto helictoglossae (Figs 38, 39). Striae radiate, areolae with hymen occlusions (Figs 39–41). Remarks:—Valve dimensions of the specimens examined in the present study have a wider size range than H. P. Gandhi in the original description- length 54.0–58.0 µm; width 14.4 µm (see Table 2). This taxon is also observed in Sr 46, collected by H. P. Gandhi from the same site at the same time and date as Sr 48. Etymology:—The specific epithet “ dharwarensis ” refers to the type locality Mugad, Dharwar district, Karnataka, where H. P. Gandhi originally collected the sample.

Luticola coloradiana, Shea, Greifenstein & Kociolek, sp. nov. (Figs 1–19) Description: In LM (Figs 1–8) valves are rhombic-lanceolate to rhombic in smaller specimens. Valves measure 23.0– 70.0 µm in length, 11.0–18.5 µm in breadth. Raphe branches are axial, along the apical axis. Isolated stigma near center of valve. Striae radiate outwards, non-uniform in appearance, often becoming smaller close to valve margin, 10–12 in 10 µm. In the SEM, the valve exterior has a rugose appearance, formed by thickened ridges running longitudinally along the apical axis of the valve and by areolae being located in depressions on the valve face (Figs 9–11). Areola density 11–14 / 10 µm. There is an elevated ridge running around the entire margin of the valve (Fig. 11). The axial area is straight, expanded slightly towards the central area, rectangular in shape and without areolae, only a single, small stigma opening (Figs 9–13). The stigma opening is smaller than the areolae. The central area may also bear numerous small depressions that do not penetrate the valve (Fig. 13). The areolar depressions and the smaller, more shallow ones around the central area may have small granules in and around them. The raphe is straight, with proximal ends bent to one side (opposite the stigma) and distal ends bent in the same direction, opposite the direction of the proximal ends. The raphe slit is bordered by a thin rim of silica (Figs 9–11, 12, 14). The mantle of the valve has a row of small poroids and a row of prominent, elongated poroids (Fig. 15). Girdle bands number 4–5 / valve and have a single row of poroids situated towards the valve. The valve interior has an expanded axial area that is developed into a central area formed by a stauros that extends nearly to the margin (Figs 16, 17). Areolae do not appear occluded internally (Fig. 16). Proximal raphe ends terminate at the base of the central area (Figs 16–18) while the distal ends terminate in small helictoglossae (Fig. 19). On one side of the central area is the stigma opening. The stigma opening is simple, round, with a short, thickened collar (Figs 16–18). Areolae are round to dash-like in shape. The valve interior, like the exterior, appears rugose (Figs 16, 17). Thick siliceous ribs extend from the margin, and on the valve face there is a line of thin, fimbriate siliceous structures that are aligned with the ribs (Figs 16, 17). Type: — USA. Colorado, Gunnison County. Unnamed wet meadow in Gunnison County, Colorado, USA. Latitude: 38.25025126, Longitude: -107.497408. Collection was made on August 2, 2021. Holotype Slide: JPK Collection (COLO!) 651052 Isotypes: To be deposited at Academy of Natural Sciences (Philadelphia) and the Natural History Museum (London). Etymology: —Named for the state of Colorado in which it occurs. Ecology: —While no other data on the physical and chemical characteristics of the collecting site were obtained, the associated diatom flora is diverse, with unnamed species of Aulacoseira Thwaites and Encyonopsis Krammer, as well as Cavinula davisiae Bahls (2013: 15) and several species of cymbelloid diatoms being present., Published as part of Shea, Rachel, Greifenstein, Jeremy & Kociolek, J. P., 2022, Valve Ultrastructure and Description of a new Luticola D. G. Mann (Bacillariophyceae) species from Colorado, USA, pp. 269-277 in Phytotaxa 554 (3) on pages 270-273, DOI: 10.11646/phytotaxa.554.3.5, http://zenodo.org/record/6831564, {"references":["Bahls, L. L. (2013) New diatoms (Bacillariophyta) from western North America. Phytotaxa 82 (1): 7 - 28. https: // doi. org / 10.11646 / phytotaxa. 82.1.2"]}

A new species of the diatom genus Luticola D.G.Mann is described from a wet meadow environment from Gunnison County, Colorado, based on light and scanning electron microscopy. The new species has rugose valves, with longitudinal interruptions in the striae. Unlike other species of the genus, L. coloradiana sp. nov. has a simple structure of the internal stigma, lacking the complex opening seen in all other species in the genus. The new species resembles L. plausibilis (Hustedt) D.G.Mann, described from Franz Josef Land in the Arctic, but differs in valve shape and density of the striae. Luticola coloradiana sp. nov. also resembles L. plausibiloides Metzeltin et al., a species described from subtropical Uruguay, but differs in striae density and the rugose nature of the valves. Further research is needed to assess if the similar species from the Arctic and subtropical South America also possess the unique stigma structure seen in L. coloradiana sp. nov.

Key to species of the genus Fogedia 1a Cells are heterovalvate.............................................................................................................................................. F. heterovalvata 1b Cells are not heterovalvate.................................................................................................................................................................2 2a Valves with lateral area.......................................................................................................................................................................3 2a Valves without lateral area..................................................................................................................................................................9 3a Central area with stauros-like transverse expansion..........................................................................................................................4 3b Central area without transverse expansion.........................................................................................................................................5 4a Striae 16-18 in 10 μm............................................................................................................................................................. F. acuta 4b Striae 9-13, Areolae 35-40 in 10 μm............................................................................................................................. F. finmarchica 4c Striae 10-12, Areolae 26-29 in 10 μm.............................................................................................................................. F. krammeri 5a External terminal raphe fissure hooked..............................................................................................................................................6 5b External terminal raphe fissure simple or slightly bent......................................................................................................................8 6a Areolae 26-29 in 10 μm............................................................................................................................................................. F. lyra 6b Areolae 35-40 in 10 μm......................................................................................................................................................................7 7a Valves 15.5-18.5 μm long, 6.5-7 μm wide.................................................................................................................. F. christensenii 7b Valves 26-37 μm long, 8-9 μm wide............................................................................................................................... F. giffeniana 8a Striae parallel in the middle of the valve................................................................................................ F. giffeniana var. yemenitica 8b Striae radiate in the middle of the valve.......................................................................................................................... F. geisslerae 9a Valves elliptic with broad apices........................................................................................................................................ F. elliptica 9b Valves with distinctively protracted apices......................................................................................................................................10 10a Striae parallel in the middle of the valve.......................................................................................................................... F. orientalis 10b Striae radiate in the middle of the valve...........................................................................................................................................11 11a Striae 12-14, Areolae 15 in 10 μm...................................................................................................................................... F. coreana 11b Striae 18-21, Areolae 21-24 in 10 μm.................................................................................................................................... F. densa

The genus Fogedia was first established in 1997 based on Navicula giffeniana as a type species. The important features of the genus were the presence of lateral area, the location of the internal raphe fissure, and the simple apical raphe endings. Later, the generic description of Fogedia has been emended with the reports of four new species to the science having the genus to include twelve members in total. A thirteenth member of the genus has been observed in tidal flats of the Yellow Sea, and here we describe the species as Fogedia orientalis sp. nov. based on observations with the light (LM) and scanning electron microscope (SEM). Regional distribution of the species in the Northeast Asia is also discussed. The new Fogedia species is morphologically similar to F. densa in terms of small cell size as wells as the absence of a lateral area, however, the density and pattern of striae are clearly different from each other. Morphological characteristics and global occurrences of the thirteen Fogedia species has been provided.

Fogedia orientalis Kim, Khim, Witkowski and Park, sp. nov. (Figs 2–15) LM observations (Figs 2–9): Valves are elliptic-lanceolate to lanceolate, with acutely-rounded protracted apices, 11.5–21 μm in length and 5.5–6.5 μm in width. External central raphe endings are punctiform, while external apical raphe endings are slightly bent to the same direction. Axial area is very narrow and linear throughout. Central area is small and square in shape, formed by two shortened striae one on each side. Typical lateral area is absent in the valve. Transapical striae parallel in the middle of the valve then becoming slightly radiate towards apices, 15–18 in 10 μm. Voigt discordance is barely discernible with LM. SEM observations (Figs 10–15): External valve face is flat with an abrupt transition to the valve mantle. Axial area is straight and symmetrical with very narrow raphe-sternum (Fig. 10). External central raphe endings are slightly expanded (Figs 10–11). The areolae and transapical striae are evenly spaced. Certain areolae near the central area exhibit different shape compared to other areolae, often being circular in shape. The raphe slit runs relatively straight from the central area to the helictoglossa which is relatively simple and small without twist (Figs 13, 15). Areolae are internally occluded by thin hymenes. Type:— Gyehwa tidal flat (35°46’ N, 126°36’ E; KO-GY), Korea. Type material collected on 6 August 2003 by Dr J. Ryu. Holotype slide deposited in MABIK (MABIK D10042862). Etymology:—The species name ‘ orientalis ’ is derived from the Latin ‘oriental’ meaning east, because the species is widely distributed in Northeast Asia. Distribution:—The species was also observed from various tidal flats on the Korean coast (a mudflat at Gyeonggi Bay, a sandflat in Saemangeum, and a mixed flat near Lake Shihwa) and Chinese coast (three sandflats at Qinhuangdao and Yingkou, in a mixed flat at Yingkou, and in a mudflat at Yancheng) of the Yellow Sea. The species was also found in a sandflat at Minamiarao in the Ariake Sea, Japan. Thus F. orientalis is probably widespread along the coast of the Yellow Sea. Differential diagnosis:—The species is similar to Fogedia densa in its valve outline, small cell size, and the absence of a lateral area. However, the pattern of striae in F. orientalis is parallel in the middle of the valve, while F. densa has a distinctively radiate striae pattern, thus the two species are readily discernable. Stria density is also much sparser in F. orientalis compared to F. densa., Published as part of Kim, Hyesuk, Khim, Jong Seong, Witkowski, Andrzej & Park, Jinsoon, 2022, A new species of Fogedia (Bacillariophyceae) from tidal flats of Northeast Asia, pp. 77-84 in Phytotaxa 554 (1) on pages 79-80, DOI: 10.11646/phytotaxa.554.1.6, http://zenodo.org/record/6809823