DEVELOPMENT OF BIOLUMINESCENCE AND OTHER EFFECTOR RESPONSES IN THE PENNATULID COELENTERATE RENILLA KÖLLIKERI

1. The development of the pennatulid coelenterate Renilla köllikeri was followed from fertilized egg to primary polyp stage, including observations on the development of effector responses such as ciliary swimming, muscular reactions and bioluminescence. 2. Ciliary swimming is first apparent in the early planula, 32 hr after the spawn. Ciliary activity persists until settlement, at approximately 130 hr. 3. Muscular reactions are first evident as local contractions in the swimmer stage (about 60 hr). Conducted contractions can be elicited at 80 hr, suggesting that a functional conduction system is present in the planula larva. At settlement, separate peduncular and anthocodial muscular responses and peristaltic contractions are evident. 4. The future photocytes first fluoresce at about 80 hr, and thereafter fluorescence intensity increases until the time of settlement. The first sign of bioluminescence follows settlement, and is delayed if settlement is prevented. Bioluminescent responses do not exhibit normal facilitation until the primary polyp stage, and responses of the preceding stages may reflect maturation of the colonial and polyp conduction systems as well as of connections between the two systems. 5. Settlement and metamorphosis are delayed when planulae are reared in containers without sand.