Cosmarium contractum var. minutum (Delp.) Coesel

Cosmarium contractum var. minutum (Delp.) Coesel *

( Fig. 2C View FIG )

Cryptogamie, Algologie 10 (3): 183 ( Coesel 1989). — Cosmarium minutum Delponte, Memorie della Reale Accademia delle Scienze di Torino, serie 2, 30: 7 ( Delponte 1877). — Ursinella minuta (Delponte) Kuntze, Revisio generum plantarum, Vol. 2: 925 ( Kuntze 1891).

Cosmarium ellipsoideum var. minus Raciborski, Pamietnik Akademii Umiejetnosci W Krakowie Wydzial Matematyczno-Przyrodniczy 10: 84 ( Raciborski 1885).

DISTRIBUTION. — Cosmopolitan. Amazon Basin: Grönblad (1945); Förster (1974); Uherkovich & Franken (1980); Cadima (2013). Western Amazonia (lowlands): no records.

DESCRIPTION

Cells 23.0-25.4 µm long, 14.0-17.0 µm wide, isthmus 6.0 µm, cells 1.4-1.6 times longer than wide. Cells hyaline, with deep median constriction, cell wall finely punctate, median sinus open. Semicells ellipsoid, with lateral margins rounded, vertically convex, apex rounded. One axial chloroplast per semicell.

REMARKS

This is a small taxon within the genus Cosmarium . As mentioned by Moresco et al. (2015) and Fadul-Souza et al. (2022), this variety differs from the type in terms of its smaller size. The size range of our specimens falls within the recorded ranges for the taxon in Grönblad (1945), Krieger & Gerloff (1962), Förster (1974), Moresco et al. (2015), and Fadul-Souza et al. (2022) from various regions in Brazil. The semicells of a morphologically similar taxon, Cosmarium moniliforme Ralfs , are semicircular. This allows these two taxa to be separated.