Stigonema Agardh ex Bornet & Flahault (1886: 62)

Mcgregor, Glenn B., 2018, Freshwater Cyanobacteria of North-Eastern Australia: 3. Nostocales, Phytotaxa 359 (1), pp. 448-450 : 448-450

Stigonema Agardh ex Bornet & Flahault (1886: 62)

Type: S. mamillosum Agardh ex Bornet & Flahault (1887: 77)

Thallus woolly or crusty, filamentous, solitary or forming cushion-like clumps or tufty colonies, with true branching. Trichomes bi- or multiseriate, uniseriate in young trichomes and at ends of branches, sometimes very thick, irregularly laterally true branched with T- and V-type branching, irregularly coiled, sometimes narrowed towards the ends, apical cell sometimes larger than adjacent cells. Sheaths thin or thick, often wide, lamellated and usually yellowish-brown in colour. Vegetative cells globose, barrel-shaped or roundly irregular, usually connected to each other by a pit connection, which may not be apparent in mature trichomes; cell content blue-green or olive-green, usually with prominent solitary granules. Heterocytes intercalary, solitary, rarely lateral. Akinetes not known. Cells divide in all planes, but crosswise fission is the most common form of division. Meristematic zones may occur in some trichome sections, in which hormogonia arise. Reproduction by hormogonia, which liberate from the ends of trichomes and branches, morphologically different from trichomes; hormogonia vary from two- to many-celled.

A world-wide genus with 66 species currently taxonomically accepted; most are aerophytic or subaerophytic, growing on the bark of trees or wet rocks; a few species are aquatic growing periphytically or epiphytically on the substrate or amongst aquatic plants. Here three species are described from north-eastern Australia; a further species is known from elsewhere in Australia. Bibliography: Skinner & Entwisle (2001), Gugger & Hoffmann (2004), Komárek (2013), Sant’Anna et al. (2013), Komárek et al. (2014), Mareš et al. (2015).

1.

-

2.

- Filaments growing freely amongst other algae, not attached to the substrate....................................................................... S. eliskae Filaments attached to the substrate.....................................................................................................................................................2 Filaments 35–75 μm in diameter, erect, fasciculate ............................................................................................................ S. informe Filaments 18–35 (–50) μm broad, irregularly branched................................................................................................... S. ocellatum