Euastrum ornatiscrobiculatum 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 : 199-200

Euastrum ornatiscrobiculatum F.M.Costa, I.B.Oliveira & C.W.N.Moura , sp. nov. ( Figs. 20–25 )

Cells in frontal view sub-elliptic, apical lobes truncate, angles decorated with 1 small spine, median incision deep, with a V-shaped opening. Basal lobes rounded, sometimes slightly tapered. Semicells with 1 supra-isthmal protrusion composed of 2 granules, 1 pair of scrobiculae and 2 granules above, 1 pair of granules on the apical lobe placed parallel to the median apical incision and 3 granules intercalated by 2 scrobicles along the lateral margins of the lobes. Semicells in lateral view ovoid and apical view elliptic. Cell wall slightly punctate. Zygospores not observed. Dimensions: Cells 27–30 μm long, 17–18.5 μm wide, polar lobe 10–12 μm wide, isthmus 4–5 μm wide.

Holotype (here designated): material numbered ( HUEFS 241804 !) deposited at Herbário da Universidade Estadual de Feira de Santana , population partially illustrated here in LM ( Figs. 20–24 ) and SEM ( Fig. 25 ) . Paratypes: HUEFS 241805, HUEFS 241806, HUEFS 241807.

Type material: BRAZIL. Bahia: Andaraí, Collected at “Marimbus do Baiano”, Pantanal dos Marimbus (Baiano Lagoon), 12° 45’ 53.8”S, 41° 18’ 38.3”W. Sample collected by F. M. Costa, G. J. P. Ramos & C. W. N. Moura.

Habitat: Periphyton; conductivity 0.10 (± 0.02 mS. cm-1); dissolved oxygen 7.3 (± 1.7 mg.L- 1); pH 7.3 (± 0.2); total dissolved solids0.04 (± 0.01 ppt); water temperature 25.5 (± 2.1 ºC); water transparency 0.76 (± 0.13 m).

Etymology: —The specific name refers to the surface ornamentation composed of scrobiculae near the margins and in the centers of the semicells.

Differential diagnosis: — Euastrum ornatiscrobiculatum differs from the other taxa in the genus by a surface decoration of 1 central protrusion composed of 2 large circular granules facing each other, and a characteristic pattern of intramarginal, alternating granules and scrobicles.

Morphologically, Euastrum ornatiscrobiculatum resembles E. dubium var. ornatum Woloszynska (1919: 49) , although the latter differs by having surface protuberances composed of three half-moon shaped granules, the absence of scrobiculae, and a shallower apical incision ( Woloszynska 1919; Růžička 1981).

The populations of E. ornatiscrobiculatum from the Pantanal dos Marimbus (Baiano Lagoon) analyzed had only reduced numbers, but exhibited relative constancy in terms of their morphological patterns, although some specimens were observed with closed apical incisions, apical margins slightly concave, and lateral lobes of similar sizes.

Euastrum praemorsum (Nordsted) Schimidle var. foersteri F.M.Costa, C.E.M.Bicudo & C.W.N.Moura , var. nov. ( Figs. 26–30 )

Cells in frontal view sub-elliptic, apical lobes with margins truncate and 1 spine angles, incision slightly open, deep, V-shaped, lateral margins decorated with 1 medium spine, forming a subapical lobe. Basal lobes with spines small at the angles. Semicells with a central protrusion composed of 3 granules, 1 pair of scrobicles above, 1 pair of granules located parallel to the apical incision. Semicells in lateral view ovoid and in apical view elliptic. Cell wall punctate. Zygospores not observed. Dimensions: Cells 36.7–38 μm long, 24.7–26.3 μm wide, lobe polar 15.5–16.8 μm wide, isthmus 5–7 μm wide.

Holotype (here designated): material numbered ( HUEFS 241811 !) deposited at Herbário da Universidade Estadual de Feira de Santana , population partially illustrated here in LM ( Figs. 26–29 ) and SEM ( Fig. 30 ) . Paratypes: HUEFS 241812, HUEFS 241813.

Type material: BRAZIL. Bahia: Andaraí, Collected at “Marimbus do Baiano”, Pantanal dos Marimbus (Baiano Laggon), 12° 45’ 52.9”S, 41° 18’ 35.6”W. Sample collected by F. M. Costa, G. J. P. Ramos & C. W. N. Moura

Habitat: Periphyton; conductivity 0.10 (± 0.02 mS. cm-1); dissolved oxygen 7.3 (± 1.7 mg.L- 1); pH 7.3 (± 0.2); total dissolved solids0.04 (± 0.01 ppt); water temperature 25.5 (± 2.1 ºC); water transparency 0.76 (± 0.13 m).

Etymology: —The specific epithet was given in honor of the German desmidologist Dr. Kurt Förster, in recognition of his contributions to our knowledge of the desmids of Bahia and Brazil.

Differential diagnosis: — Euastrum praemorsum var. foersteri differs from the other varieties of E. praemorsum by having smaller basal lobes and angle with spines small, apical lobe well-defined, long, and decorated with 1 large spine at each angle, apical incision deep and closed.

Morphologically, E. praemorsum var. foersteri resembles E. evolutum var. glaziovii (Börgersen) West & G.S. West (1898: 292) although the latter differs by having longer cells, a large subapical spine, smaller basal lobes decorated with 3–4 medium-sized spines, apical incision open and V-shaped, surface protrusion composed of 1 granule ( Prescott et al. 1977: pl. 79, fig. 4; Krieger 1937: pl. 88, figs. 1–3).

We observed variations in the basal lobes in the populations analyzed, being truncate to widely rounded, also variations in the sizes of the subapical spines (from short to medium-sized) and the apical incisions (from closed to slightly open in a V-shape). The taxon was rare in the study area.

Figures

FIGURES 15–30. Euastrum marimbusense sp. nov.: LM (15–18); SEM (19), frontal view (15, 16, 19), apical view (17), lateral view (18). Euastrum ornatiscrobiculatum sp. nov.: LM (20–24); SEM (25), head of arrows indicating scrobiculae along the lateral margins of the lobes; frontal view (20–22, 25), apical view (23), lateral view (24). Euastrum praemorsum var. foersteri var. nov.: LM (26–29); SEM (30), frontal view (26, 27, 30), apical view (28), lateral view (29). Scale Bars: 10 μm.