Planothidium novograblenovii Tseplik, Glushchenko, Maltsev et Kulikovskiy 2024, sp. nov.

Planothidium novograblenovii Tseplik, Glushchenko, Maltsev et Kulikovskiy sp. nov. (Figs. 106–127) Holotype. Slide no. kam295, in the collection of Maxim Kulikovskiy, Institute of Plant Physiology, Russian Academy of Sciences, Russia, represented here by Figure 106. Reference strain. kam295 (08127), isolated from sample 186. Type locality. Russia, Verkhniy Paratunskiy hot spring, sample 186, detritus (N 52.823.669, E 158.163.369), 18.07.2021. Description. LM (106–123). Valves small, elliptic to roundish, with broadly rounded ends. Length 6.8–10.0 μm, width 4.0–5.0 μm. Raphe straight, filiform, distal ends bent to one side. Axial area on the raphe valve narrow, linear, central area asymmetrical, wedge-shaped on one side. Striae radiate, 14–16 in 10 μm. Axial area on the rapheless valve narrow, linear. A sinus is present on one side of the valve; 1–2 striae sometimes slightly shortened on the opposite side. Striae radiate, 13–19 in 10 μm. SEM (124–127). External central raphe ends straight, slightly expanded, distal ends bent to one side and extended onto the valve mantle. Internal central raphe ends slightly turned in opposite directions, distal ends terminate in small helictoglossae. The sinus is relatively large, rounded. Axial area on the rapheless valve is ornamented very faintly with small circular depressions. Striae multiseriate, composed of 2–3 rows of areolae on both valves. Areolae small, round. Internally, the interstriae are distinctly raised. Sequence data. Partial 18S rDNA gene sequence comprising V4 domain sequence (GenBank accession number PQ066501) and partial rbc L sequence (GenBank accession number PQ074211) for the strain kam295. Etymology. The species is named in honour of Prokopy Trifonovich Novograblenov (1892–1934), a prominent Russian local historian and researcher of Kamchatka who authored the works Volcanoes of Kamchatka and Hot Springs of Kamchatka. For many years, he led the Kamchatka Museum and Local History Society, and supervised the publication of guidelines for naturalists on observing earthquakes and volcanoes and the restoration of a seismological station. Ecology. This species was isolated from a benthos sample from a hot spring. Distribution. As yet known only from the type locality.