Xanthidium mamillosum var. borgei K. Förster (1981: 247)

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 : 71

Xanthidium mamillosum var. borgei K. Förster (1981: 247) : ( Figs. 111–112 )

Cells 1.1 times wider than long; semicells about hexagonal, medial constriction deep, convex basal margins, angle with 1 pair of long, straight spines, with almost mamiliform base, arranged side by side, lateral margins slightly convex; apical margin slightly concave, angles with 1 pair of spines similar to those of the lower angles; Cell length without spines 53 μm, with spines 84 μm; cell width without spines 58 μm, with spines 90 μm, 23–24μm isthmus.

Material examined: BRAZIL, Bahia, Itaberaba, Fazenda Itaberaba. 21-I-2015, G. J. P. Ramos et al. s/n ( HUEFS 215777).

Habitat: bromeliad tanks ( Aechmea cf. lingulatoides ); T 29.9 ºC. pH 5.3. C 0.35 mS. cm-1. TDS 0.15 ppt. DO 3.6 mg.L- 1.

Notes: Xanthidium mamillosum var. borgei was the only desmid encountered in Aechmea cf. lingulatoides tanks in the region of Itaberaba, Bahia State. Those bromeliads are found in the semiarid Caatinga domain and tend to accumulate very little water; they can accumulate small amounts of moisture in the basal regions of their leaves or dry out completely. Although we only found that desmid in a single bromeliad, its mucilage sheath appears to be an important structure that allows it to survive (possibly only temporarily) in the phytotelmata by minimizing the effects of desiccation. A few specimens were observed in the sample, always showing that same morphological pattern. In Brazil, this variety occurs in central-west region ( Borge 1925) and in Amazonian region ( Förster 1969, Souza & Melo 2011). This is the first record of this variety for northeast Brazil.

Figures

FIGURES 93–112. Netrium digitus: LM (93–95); SEM (96); Pleurotaenium trabecula: LM (97–98); SEM (99–100); Staurastrum pseudosebaldi var. compactum LM (101–104), ventral view (101–103), apical view (104); Staurastrum pseudoteliferum sp. nov.: LM (105–106, 109–110); SEM (107–108), ventral view (105–107), apical view (108–110); Xanthidium mamillosum var. borgei: LM (111– 112); ventral view (111), apical view (112). Scale bar 50 μm (93–95), 60 μm (92–94), 40 μm (97), 30 μm (104–105, 111–112), 20 μm (96, 99–100), 10 μm (98, 101–108)