Macrospermum Komarék (2008: 81)

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

Macrospermum Komarék (2008: 81)

Type: M. volzii (Lemmermann) Komárek (2008: 81)

Filaments planktonic, solitary or in irregular clusters, or in fine macroscopic mats on the benthos; trichomes with symmetric or subsymmetric structure, composed of two subapical heterocytes and a third ± central heterocyte in mature trichomes; straight or irregularly coiled, with fine, colourless, diffluent mucilage, uniseriate, unbranched, ± cylindrical, constricted at the cross walls, sometimes narrowed towards ends with distinct central parts. Vegetative cells cylindrical to slightly barrel-shaped, ± isodiametric or distinctly longer than wide, with blue-green homogeneous contents, facultatively with aerotopes; apical cells rounded, conical, or narrowed and bluntly pointed. Heterocytes solitary, intercalary, cylindrical, usually wider than the vegetative cells. Akinetes widely oval, large, solitary, with smooth or sculptured exospore, rarely in pairs, always adjacent to outer heterocytes.

A genus of four species, all known from tropical regions, which can be recognised by their distinctive large akinetes which are always adjacent to one side of intercalary heterocytes. This genus has yet to be evaluated by molecular methods. Here one species is described from north-eastern Australia. Bibliography: Komárek (2008, 2013), Dwivedi et al. (2010).