Gloeotrichia Agardh ex Bornet & Flahault (1886: 365)

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

Gloeotrichia Agardh ex Bornet & Flahault (1886: 365)

Type: G. pisum Thuret ex Bornet & Flahault (1886: 366)

Filamentous, colonial; trichomes heteropolar with basal heterocytes and apical, hair-like ends with their own sheaths, radially united into gelatinous, globose or hemispherical colonies, which are microscopic up to several centimetres in diameter, olive-green, yellow-green, brown or dark blue-blackish in colour. Colonies enveloped by fine mucilage; trichomes always oriented with heterocytes towards the colony centre. Trichomes rarely falsely branched; branches rapidly separate from the mother trichome but remain parallel and radially located within the colonial mucilage forming their own gelatinous sheaths. Colonies planktonic or attached to the substratum. Trichomes uniseriate, rarely with intercalary heterocytes, constricted or unconstricted at the cross walls, straight or irregularly coiled. Sheaths always present, but sometimes gelatinized within the mucilage of colonies, especially near the apical parts of trichomes. Basal heterocytes oval or cylindrical. Vegetative cells in several planktonic species contain aerotopes. Cell division perpendicular to the long axis of the trichome, usually in a meristematic zone. Reproduction by dissociation of trichomes within colonies, and by the formation of hormogonia, differentiating after the separation of the apical hair through the formation of necridic cells, sometimes liberated from old colonies.

A worldwide genus with 28 species currently taxonomically accepted; most are known from benthic or metaphytic habitats, two species are planktonic and produce aerotopes. Five species are known from Australian freshwaters. Here two species are described from north-eastern Australia. Bibliography: Komárek (2013), Komárek et al (2014).

1.

- Trichomes 7–10 μm broad in the basal area.................................................................................................................. G. raciborskii Trichomes 4–7 μm broad in the basal area........................................................................................................................... G. natans