Pleurotaenium trabecula Nägeli (1849:104)

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 : 69-71

* Pleurotaenium trabecula Nägeli (1849:104) ( Figs 97–100 )

Cell dimensions: 450–550 μm length, 30–45 μm width, 18–25 μm isthmus.

Material examined: BRAZIL, Bahia, Santa Teresinha, Serra da Jiboia. 14-I-2015, G. J. P. Ramos et al. s/n ( HUEFS 224657), 18-VII-2015, G. J. P. Ramos et al. s/n ( HUEFS 224676), 11-IX-2015, G. J. P. Ramos et al. s/n ( HUEFS 224702), 20-XI-2015, G. J. P. Ramos et al. s/n ( HUEFS 224718).

Habitat: bromeliad tanks ( Alcantarea nahoumii ); T 26.8 (± 2.9 ºC). pH 5.8 (± 0.6). C 0.22 (± 0.16 mS. cm-1). TDS 0.12 (± 0.10 ppt). DO 7.7 (± 3.5 mg.L- 1).

Notes: Various morphological variations were observed in P. trabecula , principally semicells that were curved, but also narrow specimens that could be confused with P. ehrenbergii (Ralfs) De Bary. The latter species, however, usually shows small papillae at its apices. Although Škaloud et al. (2012) considered the culture strains identified in Europe as P. ehrenbergii and P. trabecula to be polyphyletic, and are of opinion that the presence/absence of granules at the apex does not support their mutual separation, we prefer to identify our taxon under discussion as P. trabecula (absence of papillae at the apices—traditional taxonomy) until more detailed studies can clarify their true identity. Pleurotaenium trabecula has also been reported in bromeliad phytotelmata in Rio de Janeiro State ( Sophia et al. 2004).

S taurastrum pseudosebaldi var. compactum A.M. Scott & Grönblad (1957: 44) ( Figs 101–104 )

Cells 3–radiate, 0.9–1.1 times wider than long, median constriction shallow, sinus open, processes generally short, with 3 short spines at their terminations; semicells subtrapeziform, triangular in apical view, with an intramarginal series of warts, usually curves into direction to the angles, margins between the processes almost straight, slightly crenate; chloroplast axial. Cells 43.5–46 μm long, 50–52 μm wide, 12.5–15 μm isthmus.

Material examined: BRAZIL, Bahia, Santa Teresinha, Serra da Jiboia. 14-I-2015, G. J. P. Ramos et al. s/n ( HUEFS 224663), 18-VII-2015, G. J. P. Ramos et al. s/n ( HUEFS 224683), 11-IX-2015, G. J. P. Ramos et al. s/n ( HUEFS 224693).

Habitat: bromeliad tanks ( Alcantarea nahoumii ); T 27.2 (± 3.6 ºC). pH 5.7 (± 0.5). C 0.13 (± 0.08 mS. cm-1). TDS 0.27 (± 0.31 ppt). DO 5.0 (± 1.5 mg.L- 1).

Notes: This variety has apical processes shorter than the typical variety; however, we encountered individuals with both semicells having either long or short processes (with the latter pattern being predominant). This variety was one of the rarest of all of the desmids identified in phytotelmata at Serra da Jiboia ( Table 1). The desmid Staurastrum pseudosebaldi var. compactum was previously known for the United States ( Scott & Grönblad 1957) and China ( Wei 2014). This is the third record of the variety, and the first for South America.

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)