Evidence for sexual reproduction and zoospore formation in Botryosphaerella sudetica UTEX 2629, previously assigned to the genus Botryococcus (Chlorophyceae, Chlorophyta)
Přibyl, Pavel; Cepák, Vladislav
Botryococcus sudeticus (Chlorococcales, Chlorophyta) has been recently established as a new taxon, Botryosphaerella sudetica, with respect to molecular analysis and differences in cell morphology. Here we support validity of this taxon by revealing sexual stages in the life cycle of B. sudetica and by detailed microscopic examination of cells. We found that production of zoospores and gametes is inhibited by light; motile cells emerge when B. sudetica is cultivated in darkness. Efficiency of the production of motile cells was about 50%. Both gametes and zoospores originate by the multiple division of the protoplast of the parent cell. Both motile cell types are naked, have one nucleus and a stigma spot and their size is similar. Zoospores differ from gametes in the number of flagella, that is, zoospores are biflagellate whereas gametes possess four flagella. The gametes can mate giving rise to octoflagellate, motile zygotes, but only about 1% of gametes complete fusion. This work represents the first evidence of gametogenesis and mating of gametes in B. sudetica.