CHARACTERISTICS AND REGULATION OF FISSION ACTIVITY IN CLONAL CULTURES OF THE COSMOPOLITAN SEA ANEMONE, HALIPLANELLA LUCIAE (VERRILL)

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Abstract
Permanent in vitro cultures of a clone of H. luciae from Florida [USA] were reared under different temperature and feeding regimes to identify and quantify parameters of asexual reproduction. Principle parameters of fission activity include fission rate, a delay period following a mechanical disturbance and periodic pulses of increased fission activity; all parameters are regulated by temperature and feeding frequency. A distinction is made between fission rate including the delay period (k), and fission rate following the delay period (kadj). Fission rates (kadj) ranged from 0.0162 (doubling time = 42.8 days) when fed twice/wk at 17.degree. C, to 0.0727 (doubling time = 9.5 days) when fed every 2nd day at 26.degree. C. Temperature is the foremost regulator of k. Feeding frequency has its greatest influence on periodic pulses of fission activity. Culture data indicate that asexual recruitment in natural populations of this clone is restricted by seasonal temperature; below 20.degree. C there is a sharp reduction in k. Inhibition of k by temperatures below 20.degree. C favors a transition from asexual to sexual reproduction. The pulsatile, periodic character of fission activity is prominent in laboratory cultures and suggests that such activity in natural habitats may have a phasic dependence upon tidal and photoperiodic cycles.