Euastrum fissum West & G.S.West var. nordestinum F.M.Costa, I.B.Oliveira & C.W.N.Moura, 2018

Costa, Fabiana De Matos, Ramos, Geraldo José Peixoto, Oliveira, Ivaniabatista, Bicudo, Carlos Eduardo De Mattos & Moura, Carlos Wallace Do Nascimento, 2018, Five new taxa and a new record of Euastrum (Desmidiaceae) from the Chapada Diamantina region, Bahia State, Brazil, Phytotaxa 372 (3), pp. 193-202 : 197

Euastrum fissum West & G.S.West var. nordestinum F.M.Costa, I.B.Oliveira & C.W.N.Moura , var. nov. ( Figs. 6–9 )

Cells in frontal view subelliptic, apical lobes truncate with median incision deep, closed, sometimes slightly open in a V-shape. Basal lobes retuse and slightly tapered angles. surfaces of the semicells decorated with a large and deep, circular scrobicle, bounded by 2 granules. Small granules on either side of the apical incision and near the margin of the basal lobe. Semicells in lateral view ovoid, in apical view elliptic. Cell wall slightly punctate. Zygospores not observed. Dimensions: Cells 23–26 μm long, 13–15.4 μm wide, polar lobe 7–9 μm wide, isthmus 5–7 μm wide.

Holotype (here designated): material numbered ( HUEFS 241808 !) deposited at Herbário da Universidade Estadual de Feira de Santana , population partially illustrated here in ( Figs. 6–8 ) and SEM ( Fig. 9 ) . Paratypes: HUEFS 241809, HUEFS 241810.

Type material: BRAZIL. Bahia: Andaraí, Collected at “Marimbus do Baiano”, Pantanal dos Marimbus (Baiano Lagoon), 12° 45’ 54.4”S, 41° 18’ 38.9”W. Sample collected by F. M. Costa, M. A. Santos & J. T.X. Neto.

Habitat: Periphyton; conductivity 0.09 (± 0.02 mS. cm-1); dissolved oxygen 7.9 (± 0.7 mg.L- 1); pH 7.2 (± 0.4); total dissolved solids 0.05 (± 0.01 ppt); water temperature 28 (± 1.6 ºC); water transparency 0.52 (± 0.28 m).

Etymology: —The specific epithet refers to the northeastern region of Brazil, where the taxon occurs.

Differential diagnosis: — Euastrum fissum var. nordestinum differs from the other varieties of E. fissum by having very distinct surface decorations. We could observe (under both SEM and LM) a large, deep scrobicule between the granules of the central inflation, granules located near the isthmus, and with another granule near the apical incision.

The taxon morphologically closest to E. fissum var. nordestinum is Euastrum fissum West & G.S.West (1902: 154) , although the latter differs by having surface prominences composed of three flattened granules and absence scrobicule, as can be seen in the illustrations in West & G.S. West (1902: 17–18).

The populations studied here were much reduced, although sufficient to confirm the consistencies of the observed morphological patterns. The small granules near the upper margin and papilla in the angles of the apical incision were only observed under SEM.

Figures

FIGURES 2–14. Euastrum abruptum var. chapadae var. nov.: LM (2–4); SEM (5), frontal view (2, 3, 5), lateral view (4). Euastrum fissum var. nordestinum var. nov.: LM (6–8); SEM (9). Euastrum groenbladii: LM (10–13); SEM (14), head of arrows indicating a line composed of supra-isthmal granules; frontal view (10, 11, 14), apical view (12), lateral view (13). Scale Bars: 10 μm.