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

1. Permanent cultures of a clone of H. luciae from N. W. Florida were reared under different temperature and feeding regimes in order to identifiy and quantify parameters of asexual reproduction. 2. The principle components of fission activity include fission rate, a delay period following a mechanical disturbance, and periodic pulses of increased fission activity; all components are regulated by temperature and feeding frequency. 3. A distinction is made between fission rate including the delay period (k), and fission rate following the delay period (kadj). 4. Fission rates (kadj) ranged from 0.0162 (doubling time = 42.8 days) at 17° C to 0.0727 (doubling time = 9.5 days) at 26° C. 5. Temperature is the foremost regulator of k; the greatest influence of feeding frequency was upon periodic pulses of fission activity. 6. Culture data indicate that recruitment in natural populations of this clone is restricted by seasonal temperature; below 20° C there is a sharp reduction in k. It is suggested that inhibition of k by temperatures below 20° C favors a transition from asexual to sexual reproduction. 7. 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.