Cyclotella atomus var. gracilis Genkal & K.T. Kiss in Hydrobiologia 269: 43, figs 10-16. 1993.

Bilous, Olena P., Genkal, Sergey I., Zimmermann, Jonas, Kusber, Wolf-Henning & Jahn, Regine, 2021, Centric diatom diversity in the lower part of the Southern Bug river (Ukraine): the transitional zone at Mykolaiv city, PhytoKeys 178, pp. 31-69 : 31

Cyclotella atomus var. gracilis Genkal & K.T. Kiss in Hydrobiologia 269: 43, figs 10-16. 1993.

Morphological description.

The frustule is low-cylindrical, central part of valve is slightly tangentially undulated, valves 4.6-7 μm in diameter, and a clear boundary between regional and central zones is present, 15-20 wedge-shaped striae in 10 μm, with central process (Fig. 6D, E ).

Ecology.

Planktonic in rivers, lakes, freshwater, eutraphentic ( Hofmann et al. 2018). It is regarded as an euryhaline species ( Kiss et al. 2012).

Distribution.

Cyclotella atomus var. gracilis is here first reported for the studied area, and was found at all investigated sites during this study (Table 1 ). In turn, its existence was reported in Dnipro waters ( Maystrova et al. 2007), as well as for the Danube River ( Genkal and Ivanov 1990).

This species is cosmopolitan, i.a. it was recorded for European waters ( Kiss et al. 2012; Genkal et al. 2020).

Figures

Figure 6. SEM (A-F, H) and LM images (G) of species found in the transitional zone at Mykolaiv city, valve views: A Stephanodiscus minutulus with arrows shown marginal and central fultoportulae B, C Cyclotella atomus var. atomus with arrows shown marginal and central fultoportulae D-F Cyclotella atomus var. gracilis with arrows shown marginal and central fultoportulae on D picture, only central fultoportula on E and central fultoportula and alveolae on (F) G Cyclotella choctawhatcheeana with arrow shown central fultoportulae H Cyclotella cryptica with arrows shown marginal and central fultoportulae. Scale bars: 3 μm (B, C); 4 μm (D, F); 5 μm (A, E, H); 10 μm (G).