Nervous Regulation of Luminescence in the Sea Pansy Renilla Kollikeri

Abstract

ABSTRACT Luminescence has been studied in the sea pansy Renilla kôllikeri, by means of photo-electric recording, and the mode of nervous regulation investigated. The luminescent response is under control of a non-polarized nerve net and is subject to facilitation which occurs terminally, at neuro-photocyte junctions. Facilitation is analysed in detail, and a facilitation-decay curve presented (Fig. 3). Between successive bursts of stimuli, facilitation may persist for some 10 min. Certain response parameters were measured. Latent period is o-12 sec. ; the response lasts 1 sec., and maximal intensity is reached in 0-22 sec. Conduction speed is 9 cm./sec. at 16-17° C. The refractory period of the response, as determined by high frequency stimulation, is o-2 sec. It is affected by fatigue and increases under repetitive stimulation. Under repetitive and prolonged stimulation, the animal passes into a hyper-excitatory state and luminous waves continue to arise long after stimulation has ceased. Conditions affecting this post-stimulatory discharge are examined. Comparison of facilitatory processes in quick muscular responses of sea anemones and luminescent responses of sea pens shows that they are essentially similar. From visual observations it appears that facilitation operates by recruitment of photocytes. Luminescence is of sporadic occurrence among coelenterates, and has been independently evolved on many occasions. It is suggested that its mode of regulation has been determined by the characteristics of the nerve net primarily concerned with control of muscles.