Halamphora vantushpaensis Yilmaz, Solak & Gastineau sp. nov.

Figs 2, 3, 4

LM

(Figs 2 A – M). Valves semi-lanceolate, dorsiventral with arched dorsal margin and slightly tumid ventral margin. Valve ends protracted and capitate in larger specimens (Figs 2 A – F); but less protracted and not clearly separated from the rest of the valve in smaller specimens (Figs 2 G – M), ventrally bent. Valve length 24.0–42.0 µm, valve width 4.0–5.0 µm (n = 35). Axial area very narrow, wider on the ventral side. Central area visible in larger specimens: indistinct on the dorsal side, semi-lanceolate on the ventral side. Raphe almost straight, slightly arched, appearing to be located near the median line of the valve or slightly dorsal in valve view (Fig. 2). Sometimes the proximal raphe endings can be seen to be slightly dorsally bent (Fig. 2 B). Striae hard to resolve in LM, dorsally slightly radiate over the entire valve (see SEM images for clearer demonstration of this), 27–32 in 10 µm.

SEM

(Figs 3 A – F, 4 A – F, 5 A – J). Externally, the valve face is arched, merging gently into the mantles (Figs 3 B, 4 B, C, 5 H). Raphe ledge narrow and linear, present on the dorsal side of the raphe, with a prominent groove separating it from the valve face. The proximal raphe endings are slightly expanded into central depressions and are dorsally deflected (Figs 3 B, 4 B, 5 H). The distal raphe endings are dorsally deflected and hook around to link with the groove bordering the raphe ledge (Figs 3 C, 4 C, 5 J). The striae are simple and uniseriate, containing small round or slightly elongate poroids (Figs 3 B, 4 B, C, 5 H), which are somewhat irregularly spaced (Fig. 4 B, 5 H and see also the internal views in Figs 3 E, 4 E, 5 B, E).

The internal view of the valve shows the overall structure (Figs 3 D, 5 A). The central area is easier to detect than the external area and appears symmetrical and large on the dorsal side in larger specimens (Fig. 3 E, 5 B); but very small on both sides in smaller specimens (Fig. 4 E, 5 E). Proximally, the raphe terminates within a fused central helictoglossa (Figs 3 E, 4 E, 5 E). The distal raphe endings are slightly deflected ventrally and terminate in well-developed helictoglossae (Figs 3 F, 4 F, 5 C, F). Internally, the poroids have round to elliptical internal openings (Figs 3 E, 4 E, 5 B, E). These characteristics are summarized and compared with those of similar species in Table 1.

Phycobank.

http://phycobank.org/104935.

Holotype.

Slides number SZCZEY 2167 in the collection of Andrzej Witkowski at the University of Szczecin, Poland. Valves representing the holotype population here illustrated in Fig. 2 D.

Isotype.

Slide number TR_Erciş_Van_2021 deposited in Kütahya Dumlupınar University (Türkiye).

Type locality.

Erciş Van, Turkey (39°00'07.9"N, 43°25'40.4"E) leg. Elif Yılmaz, 31 July 2021.

Etymology.

The species is named with regard to both Lake Van and the city of Tushpa, capital of the Iron Age kingdom of Urartu, which was located in the vicinity of the lake.

Distribution.

The presence of this taxon has been assessed and confirmed at four different stations around Lake Van: Ahlat (North West of the lake), Adilcevaz (North), Erciş (North East), and Edremit (South East).