Calothrix atricha Frémy (1930: 261)

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

Calothrix atricha Frémy (1930: 261) Fig. 56 A–B .

Filaments solitary or in small clusters, unbranched, straight or flexuous, up to 200 μm long, gradually tapering towards the ends, 7.5–8.0 μm wide at the base, 4.0–4.5 μm wide towards the ends. Sheaths thin, colourless, not lamellated, open at the ends. Trichomes gradually tapering towards the ends, constricted at the cross walls. Vegetative cells at the base isodiametric or shorter than broad, 4.4–6.9 μm long × 6.0–7.5 μm broad, towards the ends barrel-shaped up to 2.3 × longer than broad, 4.5–10.0 μm long × 4.0–4.5 μm wide, pinkish-red to violet in colour; apical cells bluntly rounded. Heterocytes basal, solitary spherical to slightly conical, 5.0–7.0 μm long × 3.7–7.5 μm broad. Akinetes not observed.

Specimens observed:—Porcupine Ck at Porcupine Gorge Natl Park.

Observations:—Growing in small clusters amongst submerged aquatic plants and filamentous algae in the shallows of riverine waterholes. The violet colour of mature filaments is distinctive, and consistent with the description of dried C. atricha from stagnant waters in equatorial Africa.

Figures

FIGURE 56. A–B Calothrix atricha; C–F Calothrix sp. D. Scale bars A–E = 20 μm, F = 50 μm