Lacustriella concinna Rodionova, Pomazkina & Sherbakova

Rodionova, Yelena V., Pomazkina, Galina V. & Sherbakova, Tatyana A., 2024, Two new species of the genus Lacustriella (Bacillariophyta) from Lake Baikal, Phytotaxa 652 (4), pp. 261-272 : 262-264

Lacustriella concinna Rodionova, Pomazkina & Sherbakova sp. nov.

Light microscopy (LM): ( Figs 1–15 ). Valves linearly lanceolate to elliptically lanceolate with slightly protracted rostrate apices. Valve length 37.0–82.5 μm, width 16–24 μm. External axial area narrow at apices gradually expanding into irregularly oval central area. Raphe filiform with straight central endings, terminal ends bent oppositely. Striae uniseriate parallel or slightly radial become radial towards apices, 12–13 in 10 μm. One longitudinal canal along each margin.

Scanning electron microscopy (SEM): ( Figs 16–23 ). Externally, areolae in striae round and open, irregular in the central part of the valve, 13–17 in 10 μm ( Figs 17, 18 ). Areolae bordering the longitudinal canals significantly elongated transapically, slit-like, open ( Fig. 18 ). Areolae encircling the axial and central areas enlarged. The surface of longitudinal canals is covered with uni- or biseriate rows, continuing the striae, and consisting of 1–5 small pores ( Figs 18–20 ). Areolae on the mantle transapically elongated similar to those at the border with the longitudinal canals. Proximal raphe endings lay in slightly elongated drop-shaped depressions ( Fig. 17 ). Distal raphe endings curved to opposite sides. Internally, areolae in striae are covered with hymenes, and raphe endings terminate on helictoglossae, central helictoglossae merged ( Figs 22, 23 ). The cingulum consists of two bands with a row of pores. At the same apex, the open band alternates with the closed one ( Figs 19, 20 ).

Type: RUSSIA. Lake Baikal: Northern Baikal , Olkhon isl., Cape Khoboi (53.576111 ºN, 107.8075 ºE), littoral zone at 12 m, sand sample collected by Sherbakova T.A. on June 18, 2021 (holotype: NSK0201989 housed at the Central Siberian Botanical Garden , Novosibirsk, Russia, M.G. Popov Herbarium NSK. Representative type specimen is illustrated in Fig. 2 . Isotypes: slide 0145–ВК, Limnological Institute SB RAS, Irkutsk, Russia, station 40, near the city of Baikalsk ).

Etymology: the specific epithet concinna means harmonious, proportionate.

Figures

FIGURES 1−15. Lacustriella concinna sp. nov. LM micrographs showing morphological variations of valve views. Fig. 2. Holotype. Scale bar = 10 μm.

FIGURES 16−23. Lacustriella concinna sp. nov. from type material, SEM external (Figs 16–20) and internal views (Figs 21–23). Fig. 16. Valve view. Fig. 17. Central area with proximal raphe endings and areolae in striae. Fig. 18. Slit-like areolae bordering the longitudinal canal; pores on the canal surface. Figs 19–20. Distal raphe endings, cingulum of two bands. Fig. 21. Valve view. Fig. 22. Central nodule, proximal raphe endings terminate in merged helictoglossae; areolae in striae covered with a hymen. Fig. 23. Distal raphe ending with a helictoglossa. Scale bars = 10 μm (Figs 16, 21); 5 μm (Figs 17, 19–20, 22–23); 2 μm (Fig. 18).