Lake Van diatom (Halamphora vantushpaensis), new diatom species in the highly alkaline Lake Van in Eastern Türkiye

NEWS - Lake Van diatom (Halamphora vantushpaensis Yilmaz, Solak & Gastineau, sp. nov.), a new diatom species discovered in the highly alkaline Lake Van in Eastern Turkey (Türkiye) based on light and scanning electron microscopy analysis, and a genome-skimming approach that provided access to the complete sequences of the nuclear rRNA gene cluster, mitochondrial and plastid genomes.

Lake Van is the largest soda lake in the world with saline (21.4‰) and alkaline (155 m mEq-1, pH 9.81) water. The lake has existed for 600,000 years, spanning several glacial-interglacial cycles and hosting endemic fish species.

However, studies on the phytoplankton flora of the lake, and in particular on diatoms, are still very rare. In recent years, new investigations have been carried out using an integrative approach combining light/scanning electron microscopy (LM/SEM) and molecular phylogeny derived from sequencing results.

With these data, 3 new species have been discovered and described, Nitzschia anatoliensis Górecka, Gastineau & Solak (2021), Navicula vanseea Yılmaz, Gastineau, Solak & Witkowski (2024) and Halamphora witkowskii Yilmaz.

H. vantushpaensis has semi-lanceolate valves, dorsiventral with arched dorsal margin and slightly tumid ventral margin. Valve ends protracted and capitate in larger specimens; but less protracted and not clearly separated from the rest of the valve in smaller specimens, 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.

Sometimes the proximal raphe endings can be seen to be slightly dorsally bent. Striae hard to resolve in LM, dorsally slightly radiate over the entire valve, 27–32 in 10 µm.

Externally, the valve face is arched, merging gently into the mantle. 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.

The distal raphe endings are dorsally deflected and hook around to link with the groove bordering the raphe ledge. The striae are simple and uniseriate, containing small round or slightly elongate poroids, which are somewhat irregularly spaced.

The internal view of the valve shows the overall structure. The central area is easier to detect than the external area and appears symmetrical and large on the dorsal side in larger specimens; but very small on both sides in smaller specimens.

Proximally, the raphe terminates within a fused central helictoglossa. The distal raphe endings are slightly deflected ventrally and terminate in well-developed helictoglossae. Internally, the poroids have round to elliptical internal openings.

The species is named after Lake Van and the city of Tushpa, the capital of the Iron Age kingdom of Urartu, located around the lake. The presence of this taxon has been assessed and confirmed at four different stations around Lake Van: Ahlat (northwest of the lake), Adilcevaz (north), Erciş (northeast), and Edremit (southeast).

Original research

Yilmaz E, Gastineau R, Solak CN, Górecka E, Trobajo R, Turmel M, Lemieux C, Otis C, Witkowski A, Mann DG (2024). Morphological and molecular characterization of Halamphora vantushpaensis (Bacillariophyceae, Amphipleuraceae), a new diatom species widely dispersed on the shores of the soda Lake Van (Türkiye). PhytoKeys 249: 95-114, DOI:10.3897/phytokeys.249.133205

Dlium theDlium