Euastrum bicudoi G.J.P.Ramos & C.W.N.Moura, 2019

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 : 189

Euastrum bicudoi G.J.P.Ramos & C.W.N.Moura , sp. nov. ( Figs 40–42 )

Cells somewhat longer than wide; semicells trapeziform with concave margins between the lobes; median constriction deep, with sinus open; apical incision open, V-shaped; basal lobes ornamented with 1 long spine, polar lobes with 4 spines, unequal, 2 long on the margin, divergent, 2 short in the apical incision, convergent; cell wall with a pronounced central protuberance, circular; chloroplast with one pyrenoid per semicell. Zygospores not observed. Cell dimensions: length 25–26 μm, width 20–22.5 μm, apical lobe 10–11 μm, isthmus 5–5.5 μm.

Holotype: material numbered ( HUEFS 244149 !) deposited at Herbário da Universidade Estadual de Feira de Santana , population illustrated here in LM ( Figs 40–42 ).

Etymology: The epithet is given in honor of Brazilian desmidiologist Dr. Carlos Eduardo de Mattos Bicudo for his invaluable contribution to knowledge of desmids in American continent, especially in Brazil.

Type locality and habitat characteristics: Collected at “Barragem do Dragão” Piatã , Bahia state, Brazil. Lat. 13° 05’ 48” S, Long. 41° 51’ 02” W. Sample collected by G. J. P. Ramos , C. W. N. Moura, F. M. Costa and M. A. Santos s/n ( HUEFS 244149 ) on 13 July 2017. Euastrum bicudoi occurred in periphyton ; water temperature 21ºC, pH 7.8, conductivity 10 μS. cm-1, dissolved oxygen 9.2 mg.L- 1.

Notes: The presence of elongated spines is the most notable feature of this species, which was considered rare in the study area. We have analyzed approximately 30 specimens, and all of the cells presented the same morphological pattern with considerably elongated spines on both the polar and lateral lobes.

Morphologically, Euastrum bicudoi resembles Euastrum cuspidatum var. goyazense (Kurt Först. & F.Eckert) Kurt Först. (1969: 31) , although the latter differs mainly by having 2–3 short spines on the lobes instead long spines. This morphotype is apparently typical of the tropical region of Brazil, since other similar taxa (e.g., Euastrum arciferum Borge [1918: 59] and Euastrum subtile Borge [1918: 58] ) were also described from material collected in the states of Bahia, Goiás, and Rio de Janeiro.

Figures

FIGURES 28–50. Euastrum piataense (28–34): LM (28–31), SEM (33,34), ventral view (28–30, 33), lateral view (31,34) apical view (32); Euastrum subcyclopicum var. elongatum (35–39): LM (35–38), SEM (39), ventral view (35–36, 39), lateral view (37), apical view (38); Euastrum bicudoi (40–42): ventral view (40), lateral view (41), apical view (42); Euastrum subtrilobulatum var. laeve (Figs 43–46): ventral view (43,44), lateral view (45), apical view (46); Micrasterias arcuata var. perforata (47–50): LM (47–49), SEM (50), zygospore (49). Scale bar 10 μm.