Stigonema tomentosum (Kützing) Hieronymus (1895: 166)

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 : 12

Stigonema tomentosum (Kützing) Hieronymus (1895: 166) ( Fig. 8 )

Thallus forming a black thin layer on the substrate, slightly woolly surface. Creeping filaments from which grow numerous fasciculated, more or less erect branches, similar in morphology. Creeping filaments cylindrical, uniseriate to biseriate, 15–20 µm wide. Branches rise perpendicular from the main filaments, often near one another, 12–17 µm, forming erect fascicles, usually divaricated at the apical region. Sheaths yellow-brown. Trichomes moniliform in the main filament, 12–15 µm wide, with rounded and compressed cells 6–10 µm long; and almost not constricted in the apical parts of the branches. Branches 11–15 µm wide, with shorter than wide cells, 4–10 µm long. Heterocytes intercalary arranged, short barrel-shaped up to rounded-cylindrical, generally 5–8 µm wide, 10.5–11.5 µm long. Hormogonia formed at the ends of branches, composed of 5–18 short cells, distinctly constricted at cross walls.

Habitat:— On wet wooden substrate.

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 427513) .

Notes:— This species is not very common and is rarely recorded, probably in different senses according to various authors. For this reason, the identification of this species is unclear. The fasciculation of trichomes is its main characteristic. Stigonema tomentosum grows on wet rocks and wood, but it has been recorded from very distant areas worldwide, both from temperate and tropical regions. The material from the Atlantic Rainforest corresponds quite well to the original description of this species, mainly in relation to large, flat, blackish woolly mats on a wet wooden desk. The principal characteristics of this species are the simple, densely arranged, fasciculated trichomes. In basal parts numerous creeping main filaments occur, from which parallel branches grow erect.

Stigonema crassivaginatum (Geitler) Sant’Anna, Kaštovský, Hentschke& Komárek, comb. et stat. nov. ( Figs 9 , 10 )

Basionym: — Stigonema hormoides var. crassivaginatum Geitler, Arch. Hydrobiol. Suppl. 12: 629, 1933 ( Geitler 1933). Type:— BRAZIL. São Paulo State: São Luiz do Paraitinga , 23º13’S, 45°18’W, 9 November 2002, C.L. Sant’Anna, M. T. P. Azevedo & J. Komárek (holotype: SP 427514) .

Filaments creeping, more or less straight, uniseriate, narrowed towards the ends (both trichomes and filaments), 20–25 (40) µm wide. Branching relatively rare, branches short, usually conical, 12–15 µm wide at the end. Sheaths relatively thick, distinct, delimited, stratified, yellow-brown, colorless at the end and in young branches, closed and round. Trichomes constricted at cross walls, attenuated, composed of near-regular rows of slightly compressed round cells, 12–14 µ m wide, at the ends 7–8 µ m. Heterocytes rarely hemispherical, usually barrel-shaped or shortly barrel-shaped, of the same size as the neighbouring vegetative cells. Hormogonia are formed at the end of narrowed branches, cylindrical, almost without constrictions at cross-walls.

Habitat:— On rocks.

Samples examined:— BRAZIL. São Paulo: Ecological Station “Juréia-Itatins”, 15 August 2011, C.L. Sant’Anna (SP 427307) .

Notes:— Stigonema hormoides is a very variable species and is recorded under different concepts ( Frémy 1930, Silva & Sant’Anna 1996). According to Bornet & Flahault (1886), S. hormoides var. hormoides presents subglobose cells and rarely branched subtorulose filaments that can be uni- or biseriate The tropical material from Brazil and from the Sunda Islands presents uniseriate and non-subtorulose filaments with frequent branching and compressed cells. Moreover, the typical populations of S. hormoides grow in peaty, acidic habitats in temperate regions, where this species was described, while the tropical populations were found on wet rocks. The concept of subspecific taxa in cyanobacterial taxonomy is unclear, and the taxon from Brazil and from Sunda Islands should be recombined to a status of species rank.

Figures

FIGURE 8 A–I: Stigonema tomentosum. A: Fasciculated filaments. B: Detail of biseriate filament. C: Detail of apex of branches. D: Branched filaments. E, F: Hormogonia. G: Initial stage of branching. H: Parallel erect branching. I: Branched uniseriate filaments. Scales: 10 µm A, B (use for B, C), D, E (use for E–H) and I.

FIGURE 9 A–H: Stigonema crassivaginatum. A: Branched filament with attenuated ends. B: Strictly uniseriate filaments. C: Formation of a hormogonium. D–F: Morphological variability of cells and apex. G: Sheaths with parallel lamellae. H: Sheaths with divergent lamellae. Scales: 10 µm in A (use for A–C), D (use for D–F) and G (use for G, H).

FIGURE 10 A–F: Stigonema crassivaginatum. A: General aspect of a thallus. B–D: Details of branching. E: Detail of an apex. F: Lamellated sheaths. Scales: 50 µm in A and 10 µm in B–F.