Staurodesmus convergens (Ehrenb. ex Ralfs) S.Lill

Staurodesmus convergens (Ehrenb. ex Ralfs) S.Lill

( Fig. 7G View FIG )

Acta Limnologica 3: 264 ( Lillieroth 1950). — Arthrodesmus convergens Ehrenberg ex Ralfs , The British Desmidieae: 118 ( Ralfs 1848).

Phycastrum convergens Perty, Mittheilungen der Naturforschenden Gesellschaft in Bern 1849 (164-165): 175 ( Perty 1849). — Arthrodesmus minor W. B. Turner, Kungliga Svenska Vetenskaps-Akad - emiens Handlingar 25 (5): 134 ( Turner 1893). — Staurodesmus convergens var. ralfsii Teiling, Arkiv för Botanik 6: 590 ( Teiling 1967). — Staurodesmus convergens var. laportei Teiling, Arkiv för Botanik 6: 588 ( Teiling 1967). — Staurodesmus convergens var. pumilus (Nordstedt) Teiling, Arkiv för Botanik 6: 589 ( Teiling 1967).

DISTRIBUTION. — Cosmopolitan. Amazon Basin: Grönblad (1945); Thomasson (1971); Melo et al. (2005); Souza de & Melo (2011); Cadima (2013); Cunha de et al. (2013). Western Amazonia (lowlands): Araujo (2003); Duque & Donato (1996b); Duque & Núñez-Avellaneda (2000), Núñez-Avellaneda (2008); Díaz-Olarte & Duque (2009).

DESCRIPTION

Cells 40.0-43.7 µm long, 45.0-49.7 µm wide (without spines), 70.6-73.2 µm wide (with spines); isthmus 10.5-13.0 µm. Smooth cell walls. Subellipsoidal semicells, irregularly contoured; deeply constricted, sinus widely open at the extremity, robust and strong spines directed convergently. Apical and lateral sides slightly convex. Semicells slightly different in size.

REMARKS

This taxon is considered to be very polymorphic, presenting high variability in size, semicells shape, length of spines, and spines site of insertion ( Coesel & Meesters 2013).