Cyclotella cryptica Reimann, J.C. Lewin & Guillard in Phycologia 3: 82, figs 4-11. 1963.

Morphological description.

Frustule cylindrical, the medium part of a valve slightly tangentially undulated, or flat, valve diameter is 6.4-6.7 μm, a clear boundary between edge and central zone is absent, striae wedge-shaped, 8 in 10 μm, single central fultoportula (Figs 6H, 7A).

Ecology.

Cyclotella cryptica is a planktonic species, known from marine and brackish environments, may be found in high chloride concentrations. It occurs at maximum abundance around 20 °C (Liu and Hellebust 1976; Makarewicz 1987; Mills et al. 1993). Cyclotella cryptica is a saprophilic species (Barinova et al. 2019), requires NO3 as its source of nitrogen and Ni ions in order to grow autotrophically, however is capable of heterotrophic growth in bottom water or mud enriched in glucose and known to grow mesotrophically (Oliveira and Antia 1984; Saros and Fritz 2000).

Distribution.

Valves were identified at the site in the south of Mykolaiv city in the Southern Bug River (Table 1).

It is a widespread species, recorded for Europe, North America, and Asia (Mills et al. 1993; Guiry and Guiry 2021).