Stigonema flexuosum West & West (1897: 293)

Sant’Anna, Célia L., Kaštovský, Jan, Hentschke, Guilherme S. & Komárek, Jiŕí, 2013, Phenotypic studies on terrestrial stigonematacean Cyanobacteria from the Atlantic Rainforest, São Paulo State, Brazil, Phytotaxa 89 (1), pp. 1-23 : 9-10

Stigonema flexuosum West & West (1897: 293) ( Fig. 7 )

Filaments entangled, mostly creeping on the substrate, uniseriate, only occasionally with two cells aside, more or less cylindrical, 15–20(22) µm wide. Morphology of the main filaments and branches is almost the same, branches sometimes slightly narrower, rounded at the ends. Sheaths slightly lamellate, mostly slightly brownish. Trichomes moniliforms, 13–17 µm wide. Cells rounded, usually shorter than wide, after lengthwise division almost isodiametric, 9–15 µm long. Heterocytes numerous, mostly lateral 10–13 µm wide, less frequently intercalar, with the same dimensions as the cells. Hormogonia short, cylindrical, composed of shortened cells, uniseriate, separated from sheaths at the ends of branches.

Habitat:— On wet soil.

Samples examined:— BRAZIL. São Paulo: Campos do Jordão , Mata Atlântica , 9 November 2002, C.L. Sant’Anna, M. T. P. Azevedo and J. Komárek (SP 427510); State Park of “Ilha do Cardoso”, 29 June 2010, W.A. Gama Jr. and C.F. da S. Malone (SP 401439) .

Notes:— The Brazilian populations correspond almost exactly to the original description of S. flexuosum , and the ecology is not very different (wet soils, rocky substrates, stagnant waters). However, very similar populations were often recorded from tropical regions under different names ( S. ocellatum Bornet & Flahault 1886: 69 , S. hormoides Bornet & Flahault 1886: 68 or S. hormoides var. africanum Fritsch 1923: 370 ). The taxonomy of these similar types is still unclear and should be resolved with culture studies and experimental methods.

Figures

FIGURE 7 A–F: Stigonema flexuosum. A: Detail of a biseriate filament. B: Branch after the release of a hormogonium. C: Branch forming a terminal hormogonium. D: Detail of a branch. E, F: Branched filaments with heterocytes. Scale: 10 µm in A (use for A–F).