Nostoc Vaucher ex Bornet & Flahault (1886: 181)

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

Nostoc Vaucher ex Bornet & Flahault (1886: 181)

Type: N. commune Vaucher ex Bornet & Flahault (1888: 203)

Thallus micro- to macroscopic, gelatinous, amorphous, globose or irregularly lobed, smooth or warty on the surface, filamentous or forming flat gelatinous colonies, usually with a distinct and firm surface integument. Filaments within colonies irregularly coiled and loosely or densely agglomerated, sometimes more concentrated in the peripheral area of the colony; sheaths around trichomes present, but visible usually only in the periphery of colony or in young colonies, wide, fine mucilaginous, confluent with colonial mucilage, sometimes yellowish-brown. Trichomes isopolar, the same width along the entire length, apical cells not morphologically differentiated from other vegetative cells. Vegetative cells cylindrical, barrel-shaped to almost spherical. Heterocytes solitary or in series, terminal or intercalary. Akinetes develop apoheterocytically, oval, single or commonly in series, slightly larger than vegetative cells.

A widely distributed genus of 101 species known from the benthos of freshwater lakes and reservoirs, rivers and estuaries, and many terrestrial habitats. Here six species are described from north-eastern Australia; a further three species are known from elsewhere in Australia. Bibliography: Skinner & Entwisle (2001), Hrouzek et al. (2013), Komárek (2013), Komárek et al. (2014), Joneson & O’Brien (2017).

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Mature colonies typically macroscopic, spherical, flattened, or irregularly lobate............................................................................2 Mature colonies typically microscopic, spherical to irregularly spherical, amorphous.....................................................................4 Mature colonies thin, mucilaginous, amorphous.................................................................................................................. N. linckia Mature colonies spherical to irregularly lobate..................................................................................................................................3 Colonies initially spherical, when mature, irregularly flattened, on wetted soils ............................................................ N. commune Colonies initially spherical, when mature irregularly lobate, in flowing streams....................................................... N. verrucosum Vegetative cells cylindrical...................................................................................................................................................... N. sp. A Vegetative cells barrel-shaped, isodiametric or longer than broad.....................................................................................................5 Vegetative cells 3.5–5.5 μm long × 4.1–4.8 μm wide, olive-green to yellow-brown in colour .................................. N. sphaericum Vegetative cells 2.8–6.2 μm long × 2.8–3.6 μm wide, pinkish red in colour.......................................................................... N. sp. B