BIOLUMINESCENT BEHAVIOR IN RENILLA. I. COLONIAL RESPONSES

1. Some details are given of the external morphology of the autozooids and siphonozooids and of their distribution in the colony. It is estimated that a minimum of over 6 meters of nerve net would be required to conduct excitation across an average-size colony during the passage of a wave of luminescence. 2. An account is given of the localization of luminescence in the two types of polyp and of their apparently differing behaviors in colonies collected in summer and winter. 3. In summer colonies the sharp luminous waves induced by electrical stimulation are entirely due to siphonozooids. Under strong stimulation the autozooid calices produce a long lasting glow. 4. Neuroeffector facilitation takes place uniformly throughout the colonial conduction system. Decay of facilitation requires 10-36 seconds, by different tests. There are indications that sensory adaptation in the (hypothetical) net can be local. 5. Local recording shows that the response cycle in small areas of the colony is much shorter, and its frequency response much higher, than indicated by integrative recordings of the wave response as a whole. 6. Individual siphonozooid clusters can flash repetitively in successive waves, fail to participate in every wave and vary in intensity from wave to wave. The increase in light intensity during successive facilitating waves seems due to increase in the activity of individual clusters, not to recruitment of additional clusters. There were indications of individual differences in threshold, adaptation and autoexcitation between clusters. 7. During strong repetitive electrical stimulation there may arise extra siphonozooid waves of augmented brightness, running in the same direction as the "normal" waves ( i.e., centrifugally from the electrode) or in the reverse direction. The colony may then enter an autoexcitatory state ("frenzy"), independent of external stimulation and often involving development of several excitation centers, in which waves of irregular and constantly changing form course over the rachidial surface for up to an hour.