PARTHENOGENESIS IN HORMOSIRA-BANKSII (FUCALES, PHAEOPHYCEAE)

Unfertilized eggs of Hormosira banksii maintained in culture undergo a limited degree of parthenogenetic development. The proportion of eggs showing signs of parthenogenesis is substantially lower than the 95% or more of zygotes that develop into embryos, and the rate of developm ent is slower than that of zygotes. Twenty-four hours after they are r eleased from the oogonium, 74% of unfertilized eggs secrete a cell wal l, and after 2 days 13-22% of the unfertilized eggs have polarized and germinated. One to several cell divisions occur in less than 1% of un fertilized eggs, and abnormalities such as asymmetrical divisions are common in these eggs. Development beyond this stage has not been obser ved. Paired centrioles were observed in some eggs. Previously, parthen ogenesis in the Fucales has been thought to be absent or only associat ed with abnormal experimental procedures. This is the first report of parthenogenetic development in fucoids.