VEGETATIVE REPRODUCTION AND SEXUAL LIFE CYCLE OF THE TOXIC DINOFLAGELLATE GYMNODINIUM CATENATUM FROM TASMANIA, AUSTRALIA

摘要: The toxic, chain-forming dinoflagellate Gymnodinium catenatum Graham was cultured from vegetative cells and benthic resting cysts isolated estuarine waters in Tasmania, Australia. Rapidly dividing, log phase cultures formed long chains of up to 64 whereas stationary were composed primarily single (23-41 pm long, 27-36 wide). Vegetative growth (mean doubling time 3-4 days) optimal at temperatures 14.5-20° C, salinities 23-34% light irradiances 50-300 μE·m −2 ·s −1 . sexual life cycle G. easily induced a nutrient-deficient medium, provided compatible opposite mating types combined (heterothallism). Gamete fusion produced large (59-73 μm 50-59 wide) biconical, posteriorly biflagellate planozygote (double longitudinal flagellum) which after several days lost one flagellum gradually became subspherical shape. This older stage persisted for two weeks before encysting into round, brown cyst (42-52 diam; hypnozygote) with microreticulate surface ornamentation. Resting germinated dormancy period as short under our culture conditions, resulting single, germling cell (planomeiocyte). divided form chain cells, subsequently re-established population. Implications the bloom dynamics this toxic dinoflagellate, causative organism paralytic shellfish poisoning, are discussed.