Euastrum octogibbosum Willi Krieg. (1937: 586)

Ramos, Geraldo José Peixoto, Costa, Fabiana De Matos, Santos, Maria Aparecida Dos & Moura, Carlos Wallace Do Nascimento, 2019, Taxonomic novelties, new records, and rare species of desmids from the Chapada Diamantina region, Brazil, Phytotaxa 391 (3), pp. 185-196 : 190

Euastrum octogibbosum Willi Krieg. (1937: 586) ( Figs 26–27 )

Cell dimensions: length 19,5–21 μm, breadth 13,5–15 μm, apical lobe 11–12 μm, isthmus 5–6 μm.

Habitat characteristics: Periphyton; water temperature 21ºC, pH 7.8, conductivity 10 μS. cm-1, dissolved oxygen 9.2 mg.L- 1.

Material examined: HUEFS 244149.

Notes: Krieger (1937) proposed Euastrum octogibbosum as a new name for Euastrum coralloides var. subintegrum West & G.S. West (1907: 198) based on specimens from Burma ( Myanmar), as that author considered E. coralloides an uncertain species.

Euastrum octogibbosum is a rare species, with known distributions on the Asian continent ( Krieger 1937, Hinode 1955, Scott & Prescott 1961). The main morphological features of this species are trapeziform semicells with four prominent verrucae near the margins of the lobes and a central inflation furnished with 3 verrucae arranged in a circle.

The Brazilian specimens are closest to Indonesian samples illustrated by Scott & Prescott (1961: Pl 13, Fig. 3 , as Euastrum coralloides var. subintegrum ), although the central inflation is generally composed of 3 granules instead of a single large and smooth granule as in Asian specimens. That inflation having 3 verrucae was only seen by SEM, as the inflation always appeared to be simply one large spherical protrusion under LM. Euastrum octogibbosum is reported here for the first time for Brazil.

Figures

FIGURES 2–27. Cosmarium diamantinum (2–6): ventral view (2–4), lateral view (5) apical view (6); Cosmarium dimaziforme var. concavum (7–10): ventral view (7), lateral view (8) apical view (9), cell division (10); Cosmarium pentachondrum (11–13): ventral view (11), lateral view (12) apical view (13); Euastrum bahiense (14–16): ventral view (14), lateral view (15) apical view (16); Euastrum croasdaleae var. incrassatum (17–20): ventral view (17,18), lateral view (19) apical view (20); Euastrum duplicato-verrucosum (21–25): ventral view (21,22), lateral view (23) apical view (24), zygospore (25); Euastrum octogibbosum (26–27): LM (26), SEM (27). Scale bar 10 μm.