NATURAL HISTORY OF THE HYDROCORAL ALLOPORA CALIFORNICA VERRILL (1866)

¹ Department of Zoology, University of California, Berkeley, California 94720

1. The life history of the hydrocoral Allopora californica has been studied over a two-year period. The formation of male and female gonophores is described and the maturation of sperm and eggs within these is illustrated.

2. Eggs are fertilized within the ampullae in the female colony. Subsequent larval development is described. The yearly cycle of sperm and egg maturation begins in January and culminates with release of planula larvae in November.

3. Field observations to study settlement and mortality of young colonies showed that only a very small percentage of them survive a full year. Competition for space and smothering by sediment are two main factors accounting for the high mortality.

4. The process of regeneration in the hydrocoral was studied using photography in the field combined with histological study in the laboratory. After a branch is cut the broken end has sharp edges and many damaged cyclosystems. Within a week new tissue has covered the wound, and new cyclosystems are visible after 7-8 weeks. Upward growth resumes 4-5 months after a branch has been cut.