Mallomonas okhapkinii Martynenko, Shkurina & E. S. Gusev 2024, sp. nov.

Mallomonas okhapkinii Martynenko, Shkurina & E.S. Gusev sp. nov. (Figs 2–9). Scales are oval or ovoid, measure 3.7–6.4 × 2.8–4.2 µm, and are narrowed distally. A wide posterior rim encircles approximately half of the perimeter in the posterior part of the scale. The anterior part of the scale is bordered by the narrow, thickened edge. The entire surface of the scale is covered with evenly spaced base plate pores. A thick secondary layer with internal reticulation in the form of rounded mesh covers the distal one-half to two-thirds of the scale, without papillae. One large, rimmed pore is located in the posterior region, and surrounded by a cluster of minute pores. Bristles are 9–20 µm long, smooth, and straight, with a serrated distal tip; the bristle shaft is tubular, with a longitudinal slit. Cysts unknown. Holotype (here designated): Portion of a single gathering of cells on SEM stub, deposited at the Herbarium, Komarov Botanical Institute RAS (LE), Saint Petersburg, Russia (LE A0006800). Material from meliorative channel in Vladimirskaya oblast, Russia, collected by E.S. Gusev in October 2016. Figure 6 is a representative scale from the specimen. Type Locality: Russia, Vladimirskaya oblast, meliorative channel. Latitude/Longitude: N55°35.077’ E40°26.485’. Reference DNA sample: DNA sample under the name R122 deposited at the Laboratory of Soil Zoology and General Entomology of the A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences. Genbank accession for reference strain R122: PQ415546 (nuclear SSU rDNA), PQ417903 (rbc L cpDNA) and PQ415544 (nuclear ITS rDNA). Genbank accession for other strain (R123): PQ415547 (nuclear SSU rDNA), PQ417902 (rbc L cpDNA) and PQ415545 (nuclear ITS rDNA). Etymology: the epithet is named in honor of scientist Alexander G. Okhapkin (Russia), a well-known expert in algae. Distribution:—To date, Mallomonas okhapkinii has only been observed in one site in Russia. Observations: Mallomonas okhapkinii was found at pH 6.3, a specific conductance of 42 μS cm-1 and temperature 4°C.