The life cycle of Phaeocystis (Prymnesiophyceae): evidence and hypotheses
Rousseau, V.; Vaulot, D.; Casotti, R.; Cariou, V.; Lenz, J.; Gunkel, J.; Baumann, M. (1994). The life cycle of Phaeocystis (Prymnesiophyceae): evidence and hypotheses. J. Mar. Syst. 5(1): 23-39. https://dx.doi.org/10.1016/0924-7963(94)90014-0
In: Journal of Marine Systems. Elsevier: Tokyo; Oxford; New York; Amsterdam. ISSN 0924-7963; e-ISSN 1879-1573, more
The present paper reviews the literature related to the life cycle of the prymnesiophyte Phaeocystis and its controlling factors and proposes novel hypotheses based on unpublished observations in culture and in the field. We chiefly refer to P. globosa Scherffel as most of the observations concern this species. P. globosa exhibits a complex alternation between several types of free-living cells (non-motile, flagellates, microzoospores and possibly macrozoospores) and colonies for which neither forms nor pathways have been completely identified and described. The different types of Phaeocystis cells were reappraised on the basis of existing microscopic descriptions complemented by unpublished flow cytometric investigations. This analysis revealed the existence of at least three different types of free-living cells identified on the basis of combination of size, motility and ploidy characteristics: non-motile cells, flagellates and microzoospores. Their respective function within Phaeocystis life cycle, and in particular their involvement in colony formation is not completely understood. Observational evidence shows that Phaeocystis colonies are initiated at the early stage of their bloom each by one free-living cell. The mechanisms controlling this cellular transformation are still uncertain due to the lack of information on the overwintering Phaeocystis forms and on the cell type responsible for colony induction. The existence of haploid microzoospores released from senescent colonies gives however some support to sexuality involvement at some stages of colony formation. Once colonies are formed, at least two mechanisms were identified as responsible of the spreading of colony form: colony multiplication by colonial division or budding and induction of new colony from colonial cells released in the external medium after colony disruption.
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