Representatives of the genus Stichosiphon live predominantly in fresh waterbodies epiphytic on algae and higher plants. Eight species of the genus have a tropical distribution, two species were found in central European countries, three species were described from the northwest of European Russia and one species lives in the highlands of Tibet. New species of the genus Stichosiphon, S. subarcticus is described. S. subarcticus was found in the desalinated pool at the upper littoral at Bolshoy Solovetskiy Island (Solovetskiy Archipelago, the White sea) growing on copepods. Morphological and ecological notes are given. Pseudofilaments solitary or in groups, straight or curved, uniseriate, not or sometimes slightly widened at the terminal part, mature pseudofilaments 25–55 μm long, 0.9–1.5(2.2) μm wide, exocytes and basal cells (0.6)0.85–1.45(2.2) μm long, 0.8–1.5(2.2) μm wide. This species is similar to S. sansibaricus var. marinus by short single-row and unbranched pseudofilaments, differs by width of pseudofilaments, exocyte dimensions and proportions (exocytes of S. sansibaricus var. marinus always longer than wide). Due to unstable conditions in the only known habitat salinity preferences of S. subarcticus are unclear. The location is the northernmost for this genus.
A new species of solitary Entoprocta, Loxosomella angusta sp.n., from the White Sea
