Planktic morphospecies of the cyanobacterial genus Anabaena = subg. Dolichospermum - 2. part: straight types.

Abstract

This small tropical cyanobacterial group, containing Anabaena volzii Lemmermann and a few related species (A. fuellebornii SCHMIDLE, A. unispora GARDNER, A. mysorensis GONZALVES & KAMAT), differs substantially phenotypically from all other planktic or benthic Anabaena types, mainly by the subsymmetric structure of the trichomes, type of akinete formation and restricted ecology. The taxonomic uniformity of all other Anabaenalike clusters (typical benthic Anabaena, planktic Anabaena subg. Dolichospermum, Trichormus, Aphanizomenon, Cuspidothrix) was already supported by molecular analyses. All of them also have their typical morphological markers, which are clearly different from the "Anabaena volzii - cluster". Therefore, this group can not be classified in any of the mentioned revised genera and must be described as a separate generic entity of heterocytous cyanobacteria (although they have not been sequenced to date). The new genus Macrospermum is therefore defined in my article with 4 related, morphologically distinguishable species. The generic name is selected according to the unusually large akinetes.