Nematoplaca incrustans Geitler (Nostocales, Cyanobacteria/Cyanoprokaryota): reinterpretation of the life cycle and validation of the generic status
Montejano, Gustavo; Gold-Morgan, Michele; Becerra-Absalón, Itzel
The genus Nematoplaca has only been reported once, by Geitler & Ruttner from Indonesia, therefore it has been considered a rare genus. Its only described species is Nematoplaca incrustans Geitler. Bourrelly considered Nematoplaca synonymous with Desmosiphon because both have a nematoparenchymatous habit and pseudodichotomous branching. More than 30 years later, Komárek, based on the original description, reaffirmed Nematoplaca as a genus and described its reproduction as occurring by fragmentation of trichomes and probably production of hormogonia. We found a population from Tlanchinol, state of Hidalgo, Mexico that corresponds morphologically to Nematoplaca incrustans. In our observations we recognized hormogonium-like reproductive structures, but their origin and function were quite different from those of hormogonia. These structures originated from an enlarged apical cell which divided and formed baeocytes, a new observation for the reproduction of Nematoplaca. This leads to the reinterpretation of the reproductive process and life cycle, and a reconsideration of taxonomic affinities. It is probable that other closely related genera, where hormogonia or baeocytes have been reported, have the same type of reproduction as N. incrustans. Such would be the case in Capsosira, Pulvinularia, Doliocatella and Homoeoptyche.