Hapalosiphon pumilus Kirchner ex Bornet & Flahault (1887: 61)

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

Hapalosiphon pumilus Kirchner ex Bornet & Flahault (1887: 61) Figs. 29 A–E , 30 A–E .

Thallus composed of clusters of densely entangled blue-green to olive-green coloured filaments. Filaments richly branched, flexuous to irregularly coiled (6–) 8–20 μm wide. Branches vertically divicariate, erect, often slightly narrower than the main filament. Sheaths fine, colourless to yellow-brown in colour, and thickened in mature filaments. Trichomes cylindrical, clearly constricted at the cross walls, particularly in older filaments, branches less so; cells towards the apices of branches usually very short. Vegetative cells barrel-shaped and ± isodiametric in older filaments; in branches, cylindrical and up to 2–4 × longer than wide, 6.9–12.5 (–28) μm long × 5.7–12.0 μm wide. Heterocytes isodiametric to elongated cylindrical, 7.5–18.2 (–30) μm long × 4.2–7.4 (–13) μm wide. Reproduction by the production of 14–50 celled hormogonia which arise at the ends of branches and typically contain aerotopes.

Specimens examined:—Archer R. wetland #1, Freshwater L., Great Sandy Natl Park, Cooloola Section, Boomerang L., Great Sandy Natl Park, Fraser Is. Section, Cockatoo Ck at Heathlands, Honey Eater L., Moreton Is. Natl Park, Moon Point Fens, Great Sandy Natl Park, Fraser Is. Section, Blue L., Eighteen Mile Swamp, Naree Budjong Djara National Park, North Stradbroke Is., Rainbow Beach Fens, Great Sandy Natl Park, Cooloola Section, Saucepan Spring at Eliot Ck, Swallow Lagoon, Naree Budjong Djara Natl Park, North Stradbroke Is., Tortoise Lagoon, Naree Budjong Djara Natl Park, North Stradbroke Is., Welsby Lagoon, North Stradbroke Island.

Other records:— Queensland: Bailey (1893), Bailey (1895), Cribb (1976, 1974), McLeod (1975); New South Wales: Playfair (1917); Northern Territory: Scott & Prescott (1958), Thomasson (1986).

Observations:—Common in the littoral areas of wallum lakes and peaty wetlands, where it forms conspicuous colonies on the benthos, or attached to aquatic vegetation. Masses of hormogonia have been observed in the plankton of wallum lakes during spring and early summer.

Figures

FIGURE 29. A–E Hapalosiphon pumilus; B–C Hormogonia with aerotopes. Scale bars = 20 μm

FIGURE 30. A–E Hapalosiphon pumilus; E Hormogonia with aerotopes. Scale bars = 20 μm