Mallomonas paraperfossa Ignatenko, Gusev & Yatsenko-Stepanova

Ignatenko, Marina, Gusev, Evgeniy & Yatsenko-Stepanova, Tatyana, 2024, Mallomonas paraperfossa sp. nov. (Chrysophyceae, Synurales), a new species from the shallow ephemeral ponds in the steppe zone of the Southern Urals, Russia, Phytotaxa 650 (3), pp. 277-284 : 279-280

Mallomonas paraperfossa Ignatenko, Gusev & Yatsenko-Stepanova sp. nov. ( Figs. 2–11 )

Cell dimensions unknown. Body scales are oval, 5.3–6.3 × 3.1–3.5 μm, with a dome, a V-rib, a shield, anterior and posterior flanges and a posterior rim ( Figs 2–8 ). The dome is rounded. Approximately one-half of the dome, adjacent to the shield, is smooth, with numerous tiny pores, visible on TEM. Another half of the dome is covered with fine ribs and reticulation. The shield is covered with a thick siliceous layer patterned with a reticulum of meshes forming small polygonal apertures and circular, unevenly spaced depressions (pits). The depressions are 0.2–0.3 μm in diameter, they are surrounded by a thickened ring, their number varies from 1 to 12, usually more than 4. The shield is ornamented with scattered and unevenly distributed papillae. The V-rib is rounded and slightly hooded. The anterior flanges are wide, raised above the shield, with regularly spaced fine parallel ribs joined with cross ribs forming a reticulum of rectangular meshes. The posterior rim is relatively narrow, encircles about one-third of the scale perimeter and has internal struts. The posterior flange is wide and smooth. The apical scales ( Figs 9–11 ) have the same basic design as the body scales but are smaller in size (4.0–5.1 × 3.0–3.3 µm) and asymmetrical. The V-rib on the apical scales is asymmetrical, extending further along the left side of the scales where it is adjacent to the dome. The bristles are short, 5.0–6.5 µm, curved, with tiny, barely noticeable teeth on the curved side. Cysts were not observed.

Holotype:—Portion of a single gathering of cells on SEM stub number 54_I_1 deposited at the Herbarium of the Steppe Institute of the Ural Branch of the Russian Academy of Sciences, Orenburg ( ORIS). Material is from the Lake Liman (“Svetlinskii” Biological Reserve) sampled by M.E. Ignatenko on 03 May 2023. Figure 5 is a representative scale from the type specimen.

Type locality:— RUSSIA: Orenburg region, Lake Liman (“Svetlinskii” Biological Reserve) . 51°02ʼ19”N, 60°47ʼ09”E. 03 May 2023.

Etymology:—the epithet “ paraperfossa ” indicates a close resemblance to the ultrastructure of the scales of M. perfossa K.H. Nicholls (1989: 294) .

Distribution:—To date, M. paraperfossa has been observed in two neighbouring localities in Russia. In addition to the type locality, it has been found in another unnamed water body of a similar type (51°02ʼ17.4”N, 60°47ʼ15.0”E)

Observations:— M. paraperfossa was found in small, shallow, ephemeral water bodies within pH range of 7.0–8.6 and temperature 14.2–14.8 ℃.

Figures

FIGURES 2–11. Mallomonas paraperfossa sp. nov. Figure 2. Whole cell, SEM. Figures 3–4. Body scales, TEM. Figures 5–8. Body scales, SEM. Figures 9–10. Apical scales, SEM. Figure 11. Apical scale, TEM. Scale bars: 2 μm.