Cosmarium pseudomagnificum var. brasiliense (Kurt Först. & Eckert) Kurt Först.

Cosmarium pseudomagnificum var. brasiliense (Kurt Först. & Eckert) Kurt Först. *

( Fig. 2I, J View FIG )

Algological Studies / Archiv für Hydrobiologie, Supplement 28: 241 ( Förster 1981). — Cosmarium pseudomagnificum f. brasiliense Kurt Förster & Eckert, Revue Algologique, Nouvelle Série 7 (1): 74 ( Förster 1963).

DISTRIBUTION. — Brazil, Bangladesh. Amazon Basin: Förster (1969); Thomasson (1977). As C. pseudomagnificum f. brasiliense : Förster (1963); Thomasson (1971). Western Amazonia (lowlands): no records.

DESCRIPTION

Cells 71.7-84.9 µm long, 55.4-66.8 µm wide, isthmus 24.7-30.6 µm, apex 20.2-20.4 µm, cells 1.23-1.31 times longer than wide. Cell wall with granules, punctuated. Cells are large with deep median constriction; lineal narrow median sinus, slightly widened at apex. Semicells are pyramidal-truncated, with convex lateral margins, with basal sub-rectangular corners and rounded apical corners. Apex broadly truncated, straight. Semicell lateral margins with granules (between 22 and 34); no granules were observed along the apical straight margin of each semicell. Two chloroplasts per semicell.

REMARKS

Our specimens coincided with those described originally as C. pseudomagnificum f. brasiliense by Förster (1963) and those reported in Förster (1969) as C. pseudomagnificum var. brasiliense for the Amazon, and with those in Biolo (2016) for the São Paulo State in Brazil by showing cells with similar shapes and size, although our specimens’ size range is slightly larger than those of Biolo (2016) (76-81 µm L, 57-59µm W). This species can be confused with Cosmarium binum Nordstedt but differs from it by having a truncated apical margin with no granules, while in C. binum , apical margins are convex with granules ( Biolo 2016). Also, C. binum cells are smaller in size and hold a smaller number of lateral granules on each semicell, as described for specimens from Bolivia ( Thérézien 1986), and Namibia ( Grönblad & Croasdale 1971).