Stigonema cf. minutum Hassall ex Bornet & Flahault (1886: 72)

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 : 7-8

Stigonema cf. minutum Hassall ex Bornet & Flahault (1886: 72) ( Figs 4 , 5 )

Main filaments mono or biseriate, composed by rows of cells, 15–35 µm wide, with firm, delimited, brownish sheaths. Branches are morphologically the same as the main filaments, slightly and continually narrowed at the end, often ending in monoseriate parts, 15–30 µm wide. Trichomes moniliform, 12–30 µm wide, with compressed or irregularly rounded cells, 6.5–10.0 µm long, terminal cells sometimes slightly elongated and rounded at the end. Lateral heterocytes rounded, intercalary compressed, with the same dimensions as the cells. Hormogonia develop at the ends of branches, usually 4–8 cells.

Habitat:— On lateritic surface of termites nests, on the soil and on wet rocky surfaces.

Samples examined:— BRAZIL. São Paulo: Campos do Jordão, Horto Florestal , 9 November 2002, C. L. Sant’Anna, M. T P. Azevedo and J. Komárek, (SP 427507, SP 427509, SP 427511); State Park of “Ilha do Cardoso”, 29 June 2010, W.A. Gama Jr. and C.F.S. Malone (SP 401436) .

Notes:— This species is considered cosmopolitan in unpolluted soil habitats and on rocky substrates ( Geitler 1932). As other commonly distributed species, it has a great morphological variability and has been described under various concepts. We identify this species in the original sense, corresponding to Geitler (1932). The Brazilian populations are similar to S. minutum Bornet & Flahault (1886: 72) according to descriptions in the literature, but there are doubts about their identity in European populations. Even within the Brazilian populations, there are slight differences, indicating that this group requires a revision comparing the tropical/subtropical populations with those from temperate regions.

Figures

FIGURE 4 A–J: Stigonema cf. minutum. A–G: General aspect of a thallus. H: Branches forming hormogonia at the ends. I: Young filament. J.: Detail of apex with epiphytic filament of Heteroleibleinia sp.. Scales: 10 µm A (use for A–D) and E–J.

FIGURE 5 A–F: Stigonema cf. minutum. A: General aspect of a thallus. B: Unilateral branching. C–D: Branches after releasing hormogonia. E–F: Details of main filaments. Scales: 10 µm.