Gloeotrichia raciborskii Wołoszyńska (1912: 687)

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

Gloeotrichia raciborskii Wołoszyńska (1912: 687) Fig. 26 A–E .

Thallus gelatinous, olive-green to brown in colour, colonies small spherical, attached to macrophytes or the substratum, later free floating, irregularly globose, up to 3–5 cm in diameter. Filaments long,> 800 μm, tapered from a spherical basal heterocyte, radially arranged from the colony centre. Trichomes clearly constricted at the cross walls, 7–10 μm wide in the basal area, narrowing to long, hair-like cells 2–6 μm broad. Vegetative cells barrel-shaped, slightly shorter or longer than broad. Heterocytes spherical, basal, 10–14 μm in diameter. Akinetes cylindrical, long ellipsoidal with widely rounded ends, arising from several vegetative cells, 10–60 μm long × (12–) 14–25 μm broad, with colourless to dull-brown coloured exospore.

Specimens examined:—Einasleigh R. at the Beach, Blacks Ck at Whitefords.

Other records:— Queensland: Baker & Fabbro (1992) .

Observations:—Colonies growing on sandy substrate amongst submerged aquatic vegetation, or sometimes free-floating in the littoral areas or backwaters of tropical streams and rivers. A variable species, with several subspecific taxa described.

Other species known from Australia: G. echinulata P.G. Richter , Victoria, Entwisle (1994); G. pisum Thuret ex Bornet & Flahault, SE Queensland, McLeod (1975); G. raciborskii f. lillienfeldiana (Wołoszyńska) Geitler, Ling & Tyler (2000) .

3. HAPALOSIPHONACEAE

Hapalosiphonaceae Elenkin (1916: 278, 280)

Type: Hapalosiphon Nägeli ex Bornet & Flahault (1886: 53)

Filamentous, thallose; composed of true-branched filaments, with all filaments and branches morphologically similar. Trichomes unseriate, divicariate, but not morphologically divided into main trichomes and branches, often constricted at the cross walls, moniliform, but usually ± cylindrical, true-branched with T-, V, and Y-type branching. Branches cylindrical, or less frequently narrowed towards the ends, rarely attenuated to hair-like cells. Vegetative cells cylindrical, barrel-shaped or irregularly rounded; apical cells rounded. Heterocytes intercalary, barrel-shaped or spheroidal. Akinetes absent. Reproduction by production of hormogonia.

A cosmopolitan family of 13 genera; four genera and six species are known from freshwater habitats of north-eastern Australia.

Figures

FIGURE 26. A–D Gloeotrichia raciborskii; E Spherical colonies sitting loosely on the sediment in the littoral zone of a tropical river. Scale bars A = 50 μm, B–D = 20 μm