Encyonopsis indonesica Kapustin, Kulikovskiy & Kociolek, 2021

Kapustin, Dmitry A., Glushchenko, Anton M., Kociolek, John P. & Kulikovskiy, Maxim S., 2021, Encyonopsis indonesica sp. nov. (Bacillariophyceae, Cymbellales), a new diatom from the ancient lake Matano (Sulawesi, Indonesia), PhytoKeys 175, pp. 1-11 : 1

Encyonopsis indonesica Kapustin, Kulikovskiy & Kociolek sp. nov. Figs 1 , 2 , 3 , 4

Holotype

( here designated): MHA 01105 . Fig. 1B illustrates the holotype.

Type locality.

Indonesia, Island of Sulawesi, Lake Matano , 02°28.433'S, 121°15.710'E, leg. I. I. Ivanov, 14.XI.2010 .

Etymology.

The specific epithet refers to the type locality from Indonesia .

Description.

LM (Fig. 1A-J ). Valves dorsi-ventral, semi-lanceolate, with a slightly convex dorsal margin and a nearly straight ventral margin. Apices slightly protracted, cuneate to slightly rostrate. Axial area very narrow, following the course of the raphe and central area not expressed. Raphe undulate. Striae indistinct in LM. Length 17-29 µm (21.9 ± 3.3; n = 16), breadth 3-4 µm (3.4 ± 0.3; n = 16), length/width ratio 5.7-7.4 (6.5 ± 0.6; n = 16).

SEM (Figs 2 - 4 ). External valve face occasionally covered with siliceous verrucae and numerous siliceous ribs of different lengths mostly aligned along the apical axis (Fig. 2A-F ). Valve face delineated from the mantle by a thickened marginal ridge. Raphe distinctly undulate, with the proximal raphe ends deflected slightly towards the dorsal margin and the distal ends hooked strongly to the ventral side (Fig. 3E, F ). Raised sterna border the raphe branches. Striae almost parallel at the valve center becoming weakly radiate towards the apices, 34-36 in 10 µm. Striae composed of 2-4 areolae on the ventral side and 5-6 areolae on the dorsal side. Areolae rounded and unoccluded, being occasionally slightly smaller near the valve margins, 50 in 10 µm. Internally, areolae rounded or transapically elongated located in a shallow groove. Internal proximal raphe ends obscured; distal raphe ends terminate in well-developed helictoglossae (Fig. 4A-E ). A thin, plate-like silica thickening present between helictoglossa and apices (Fig. 4F, G ).

Figures

Figure 1. A-J Encyonopsis indonesica sp. nov. (LM). Size diminution series showing variation in valve outline B holotype specimen. Scale bar: 10 μm.

Figure 2. A-F Encyonopsis indonesica sp. nov. (SEM). External view A-D whole valves showing morphological variability in external ornamentation E, F central area with dorsally deflected proximal raphe ends. Note the thickened marginal ridge, longitudinal ribs and verrucae on the valve surface. Scale bars: 2 µm (A, D), 2.5 µm (B, C), 1 µm (E, F).

Figure 3. A-F Encyonopsis indonesica sp. nov. (SEM). External view A central area B, C valve ends. Note a hyaline area along the raised sternum D a part of a raphe with transapical ribs on the valve surface E, F valve ends with strongly hooked distal raphe fissures. Scale bars: 1 µm (A, C, D, E), 2 µm (B), 0.5 µm (F).

Figure 4. A-G Encyonopsis indonesica sp. nov. (SEM). Internal view A-C whole valve D, E central area with rounded or elongated areolae located in a transapically elongated grooves F, G valve ends with typical helictoglossa. Note a thin, plate-like silica thickening present between helictoglossa and apex. Scale bars: 2 µm (A, C), 2.5 µm (B), 1 µm (D, E), 0.5 µm (F, G).