ibclogo XVI International Botanical Congess


Abstract Number: 4980
Session = 4.15.5


MORPHOLOGY AND EVOLUTION OF SEXUAL REPRODUCTION IN THE COLONIALVOLVOCALES.


H. Nozaki, Univ. of Tokyo, Japan


Sexual reproduction is diverse within the colonial Volvocales. The four-celled alga Tetrabaena is similar to Chlamydomonas reinhardtii in that only one of the two conjugating isogametes bears a tubular mating structure and four separate gone cells are released from the germinating zygote. In most of other isogamous colonial Volvocales, however, both of the two conjugating gametes have a tubular mating structure and germinating zygotes give rise to a single gone cell (Pandorina etc.) or a four-celled germ colony (Gonium). The anisogamous/oogamous genera (Eudorina, Volvox etc.) exhibit sperm packets and a single gone cell. Evolutionary significance of such differences in sexual reproduction is discussed on the basis of the cladistic analysis of morphological data as well as of our recent molecular phylogenetic analyses of multiple chloroplast genes.


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