THE LIFE CYCLE OFPEACHIA QUINQUECAPITATA, AN ANEMONE PARASITIC ON MEDUSAE DURING ITS LARVAL DEVELOPMENT

Abstract

1. Peachia quinquecapitata kept in sea water tanks at the Friday Harbor Laboratories were induced to spawn. The egg is 120 µ in diameter and is covered with spines 20 µ in length. 2. Cleavage leads to a hollow blastula which becomes ciliated. As the cilia appear the spines become shorter and disappear. 3. Gastrulation is by invagination. The planula stage is reached when the gastrula develops an apical tuft of long cilia. 4. A swimming planula can be ingested by the medusa Phialidium gregarium. After ingestion the larva begins to grow and differentiate. Planulae which did not get ingested would not develop in the laboratory. 5. The larvae remained endoparasitic for an average of 11 days and probably were feeding on material in the gatrovascular cavity of the host medusa. 6. After 11 days the larvae became ectoparasitic and fed on the gonads of the host medusa. After an average of 31 days of ectoparasitism anemones had acquired their adult characteristics and dropped off the host medusa to become free-living. 7. During the ectoparasitic phase the larval anemones could transfer from one host medusa to another in the laboratory cultures. Transfer has not been observed in nature but is reasoned to occur there.