Mallomonas getseniae (Voloshko) Bessudova, 2023

Bessudova, Anna & Likhoshway, Yelena V., 2023, New observations on Mallomonas getseniae comb. et stat. nov. (Chrysophyceae, Synurales), Phytotaxa 626 (3), pp. 213-218 : 214

Mallomonas getseniae (Voloshko) Bessudova comb. et stat. nov. ( Figs 1–13 )

Basionym: Mallomonas striata var. getseniae Voloshko. 2009 . Botanicheskiy Zhurnal 94(7), 1073–1074, fig. 3.

Description: —The body scales are oblong and oval in shape, with lateral incurvings 6.2–8.0 × 3.0–5.0 μm in size ( Figs. 1–6 ). Body scales possess a posterior rim, a posterior flange, a V-rib, anterior ribs and flanges, and a dome. The dome is triangular or subcircular with labyrinth-like reticulation. The shield is marked with 9–17 transverse ribs that are either located in the anterior part or completely cover the shield. The group of 8–18 pores located in the angle of the V-rib while other area of the shield is devoid of base plate pores. The V-rib is hooded. The anterior flanges are welldeveloped, wing-like, with wavy edges and 3–7 closely spaced struts on each side. The anterior submarginal ribs are short. The posterior rim is smooth on the surface. The posterior flanges are wide with approximately 17–24 struts and irregularly spaced large pores (up to 0.065 μm). Caudal scales 4.5–4.8 × 2.1–2.4 μm in size, possess a posterior rim, a posterior flange, a V-rib and anterior flanges ( Fig. 7 ). The bristles are tubular, 7.3–23.4 μm long, straight or slightly curved. The distal end of the bristle is widened. The tip is bifurcated with unequal diverging pointed branches. One branch is shorter (0.22–0.5 μm), whereas the other is longer (1.30–1.70 μm) ( Figs. 8–13 ). Cysts are unknown.

Observations: — Mallomonas getseniae was found of the pelagic part of Lake Baikal in samples from the bottom surface of ice in March (2022) at stations No. 8 and 12 ( Bessudova et al. 2023) and in samples in May-June 2016 ( Bessudova et al. 2017), June 2020, 2021 and 2022. The samples parameters were: pH = 7.65–8.1, T = 0.1–6.3 ° C and EC 25 = 143.0–153.2 µS· cm−1 values( Bessudova et al. 2017, Bessudova et al. 2023).

Figures

FIGURES 1–7. Scales of Mallomonas getseniae comb. et stat. nov. from Lake Baikal. Figure 1–5. Body scales; Figure 6. Body scale, undersurface view. Figure 7. Caudal scale without wing-like struts on anterior flanges and without a dome. SEM. Scale bars: 4 µm.

FIGURES 8–13. Scales and bristles of Mallomonas getseniae. SEM. Scale bar: 9, 10—2 µm; 13—5 µm; 8, 11, 12—10 µm.