Cosmarium majae Strøm (1922:131)

Ramos, Geraldo José Peixoto, Bicudo, Carlos Eduardo De Mattos & Moura, Carlos Wallace Do Nascimento, 2018, Some new, rare and interesting desmids from bromeliad phytotelmata in Brazil, Phytotaxa 346 (1), pp. 59-77 : 63

Cosmarium majae Strøm (1922:131) ( Figs 26–33 )

Cell dimensions: 7.5–9 μm length, 5–7 μm width, 3.5–5 μm isthmus, 11–13 μm zygospore.

Material examined: BRAZIL, Bahia, Santa Teresinha, Serra da Jiboia. 14-I-2015, G. J. P. Ramos et al. s/n ( HUEFS 224655), 18-VII-2015, G. J. P. Ramos et al. s/n ( HUEFS 224673), 11-IX-2015, G. J. P. Ramos et al. s/n ( HUEFS 224691), 20-XI-2015, G. J. P. Ramos et al. s/n ( HUEFS 224719).

Habitat: bromeliad tanks ( Alcantarea nahoumii ); T 25.2 (± 2.9 ºC). pH 5.8 (± 0.5). C 0.17 (± 0.15 mS. cm-1). TDS 0.08 (± 0.07 ppt). DO 6.9 (± 2.3 mg.L- 1).

Notes: This species is known from only three states in Brazil: Bahia ( Oliveira et al. 2016), São Paulo (Araújo & Bicudo 2006), and Amazonas ( Förster 1974). It was observed in the phytotelmata of bromeliad specimens at Serra da Jiboia with a variable sinus, ranging from V-shaped to U-shaped, the former being the most common. As those variations occurred within the same population, and included cells with intermediate characteristics, we consider them as representing the phenotypic plasticity of a single taxon.

Those variations could lead to taxonomic confusion, however, as there are several species of Cosmarium with similar morphologies. According to Coesel & Krienitz (2008), a more precise identification of these tiny Cosmarium will require finding zygospores, which can be very different from one species to another. Due to the presence of spherical zygospores with smooth walls, and in light of the morphological features of the cells, we considered that taxon to be Cosmarium majae

Figures

FIGURES 26–48. Cosmarium majae: LM (26–33); SEM (33), ventral view (27, 29–31, 33), apical view (26), lateral view (28) and zygospore (32); C. oliveirae: LM (34–37); SEM (38), ventral view (34–35, 38), apical view (36), lateral view (37); C. pachydermum var. aethiopicum: LM (39–42); SEM (43), ventral view (39–40, 43), lateral view (41), apical view (42); C. pseudoconnatum: LM (44–47); SEM (48), ventral view (44–45, 48), apical view (46–47). Scale bar 10 μm (26–32, 34–38, 44–47), 5 μm (33), 20 μm (39–43).