Comparison of vegetative and specialized (heterocytes and akinetes) cells among four genera of nitrogen fixing Cyanobacteria

DE TEZANOS PINTO P.; KUST A.; DEVERCELLI M.; KOZLEKOVÁ (ZAPOMELOVÁ) E.

Kastoria

Workshop; 17th Workshop of the International Association of Phytoplankton Taxonomy and Ecology; 2014

International Association of Phytoplankton Taxonomy and Ecology

Species within Nostocaceae are able to differentiate heterocytes (nitrogen fixation) and akinetes (resting structure) from vegetative cells. These specialized cells vary in size and shape, and in their position (either adjacent or distant to each other; a species-specific trait). We collected information on vegetative and specialized cells of 106 species within Anabaena, Dolichospermum, Sphaerospermopsis and Chrysosporum (which until recently were all considered Anabaena) using updated literature (Komarek, 2014). We calculated cell volumes following Hillebrand et al. (1999) and relate and compare them (statistical regressions and ANCOVAs) among genera. Most of the species belong to Anabaena (59), followed by Dolichospermum (38), Sphaerospermopsis (5) and Chrysosporum (4). Out of 106 species, 64 have akinetes distant from the heterocytes, 32 adjacent ?including all species within Sphaerospermopsis-, and 10 either adjacent or distant. Allometric relationships showed positive linear relationships for all cell types. Vegetative cells in Anabaena (non-aerotopated) are significantly smaller than the aerotopated genera (Dolichospermum, Sphaerospermopsis and Chrysosporum). Heterocytes, however, are similar in size across genera, and the most frequent shape is spherical. This may reflect a constraint in size, and shape, for efficient nitrogen fixation. Akinetes in Anabaena are significantly smaller than in Dolichospermum, evidencing differences between non-aerotopated and aerotopated specimens. Akinetes in most species are cylindrical (53), followed by ellipsoid (40) ?including all four Chrysosporum species?, while very few are spherical (12) ?including all five Sphaerospermopsis species?. The low frequency of spherical akinetes may indicate a higher cost of forming this type of akinete, compared to cylindrical and ellipsoid shapes. Our literature research allows comparing metadata, which can be used to discuss possible links between differences in the morphology, ecology and physiology of these Cyanobacteria.