Skeletonema subsalsum (A. Cleve) Bethge in Ber. Deutsch. Bot. Ges. 46(5): 343, pl. 2, figs 1-11. 1928.

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

Skeletonema subsalsum (A. Cleve) Bethge in Ber. Deutsch. Bot. Ges. 46(5): 343, pl. 2, figs 1-11. 1928.

Basionym.

Melosira subsalsa A. Cleve in. Arch. Hydrobiol. 7: 509, fig. 1. 1912.

Morphological description.

The frustule is cylindrical, valves are flat or slightly convex, diameter 7.8-12.7 μm (Fig. 5B ). Frustules are connected with marginal flat-spoon fultoportulae providing a very close connection between valve mantles (Fig. 5C, D ).

Ecology.

Planktonic taxon, preferring low salinities, usually occurring in salinities up to 15‰, recorded mainly for the brackish waters, however, is known from rivers, lakes, inland seas, coastal waters, and marshes, and often associated with eutraphentic conditions, temperate taxon, alkaliphilic ( Hasle and Evensen 1975; Sarno et al. 2005; Hofmann et al. 2018). In addition, in the DAISIE database Skeletonema subsalsum is considered to be an invasive species for Russia’s and Ireland’s water bodies ( Kaštovský 2010; Korneva 2014) but is not listed in the Handbook of alien species in Europe (2009).

Distribution.

This taxon was found at the site of Mykolaiv city in the Southern Bug River (Table 1 ). Skeletonema subsalsum is widely distributed in Ukrainian waters, known from the Dnipro River in its freshwater reservoirs, in estuaries connected to the Black Sea and from coastal waters of different river basins as well as Crimea coast.

It is a cosmopolitan species, known from the Boreal, Europe (Finland, Germany, Ireland, Italy, the Netherlands, Romania, Russia, Sweden, Ukraine), North America (Canada, USA); Baltic, Black and Caspian Seas. ( Gibson et al. 1993; Krammer and Lange-Bertalot 2000; Tsarenko et al. 2009; Genkal et al. 2020).

Figures

Figure 5. SEM images of species found in the transitional zone at Mykolaiv city (A, B, E-H valve views, C, D girdle views): A Minidiscus proschkinae with arrows showing rimoportula and marginal fultoportula B-D Skeletonema subsalsum with arrows showing marginal fultoportulae E Stephanodiscus hantzschii with arrow shown spines F Stephanodiscus makarovae with arrows showing marginal and central fultoportulae G, H Stephanodiscus minutulus with arrows showing spines and central fultoportula. Scale bars: 3 μm (A); 4 μm (B, F, H); 5 μm (C, D, G); 10 μm (E).