Mallomonas kornevae E. S. Gusev, Martynenko, Hoan Tran & Podunay 2024, sp. nov.

Mallomonas kornevae E.S. Gusev, Martynenko, Hoan Tran & Podunay sp. nov. (Figs 5–6, 18–26) Cells are ellipsoidal, 11–16 × 6–8 μm, covered with overlapping scales and a few curved bristles associated with the apical scales. Three types of scales have been observed: apical domed collar scales, domeless body scales and small rear scales with spines. The body scales are rhomboidal, slightly asymmetrical, 2.2–4.1 × 1.2–2.5 μm. The shield and anterior flanges are ornamented with numerous papillae. There are no clearly defined anterior submarginal ribs on the scales. Anterior flanges are slightly raised above the shield and usually have 2–3 rows of papillae along the edge. The shield is patterned with densely spaced papillae except for an area in the angle of the posterior submarginal rib without a secondary siliceous layer. Inner polygonal reticulation of the secondary siliceous layer can be present on some scales but is usually absent. The posterior submarginal rib is well developed. There is a triangular or oval area in the angle of the posterior submarginal rib, lacking a secondary layer, which contains from 3 to 10 rimmed pores on the base plate, usually 3–5. The posterior rim is smooth. The posterior flange is narrow and smooth. The collar scales are asymmetrical, elongate and have a broadly rounded proximal end and narrower distal end, 3.0–4.8 × 1.8–2.8 μm. Ornamentation on the shield and flanges is the same as that found on the body scales. The posterior submarginal rib on the “dorsal” side is well developed, connected with the dome. An additional short submarginal rib (anterior) departs from the dome on the “ventral” side; sometimes, it can be connected with the posterior submarginal rib. There are up to 12 rimmed base plate pores in the angle of the posterior submarginal rib, usually 5–6. The dome on the collar scales is partially ornamented with papillae and has a sharply pointed peak and serration at the apical part. The rear scales are 1.2–2.2 × 0.8–1.8 μm, similar in structure to the body scales, but more oval and asymmetrical and often bearing a spine. Bristles are 6–11 µm long and curved. On the convex side of the bristle shaft, there is a serration formed by small teeth. Cysts are not observed. Holotype (here designated): Portion of a single gathering of cells on SEM stub No. 494 Yu deposited at the Herbarium of the Steppe Institute of the Ural Branch of the Russian Academy of Sciences, Orenburg (ORIS). Material from unnamed water pool near Bau Sen Lake, Thua Thien Hue Province, Vietnam, collected by E.S. Gusev on the 24 th of May, 2019. The strain was isolated by Yu.A. Podunay. Figure 18 (scale on the right) is a representative scale from the type specimen. Type Locality: Unnamed water pool near Bau Sen Lake, Thua Thien Province, Vietnam. Latitude/Longitude: N16° 34.177’, E107° 26.608’. Authentic strain: Representative living and fixed strain 494Yu and DNA sample deposited at the Collection of the A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences. Genbank accession numbers for reference strain (494Yu): PQ677574 (nuclear SSU rDNA), PQ673578 (rbc L cpDNA) and PQ677565 (nuclear ITS rDNA). Genbank accession numbers for other strains are listed in the Table 1. Etymology: the species epithet is named in honor of scientist Liudmila G. Korneva (Russia), a well-known expert in algae for her contribution to the study of chrysophytes. Distribution: In addition to the type locality, this species has been observed in other regions of Vietnam (Tables 1, 2). Mallomonas kornevae was found at wide ranges of environmental parameters: pH from 5.5 to 7.5, specific conductance from 31 to 480 µS cm-1, and temperature 25–34 ºC (Tables 1, 2).