Observations on Luminescence in Renilla (Pennatulacea)

Abstract

1. Luminescent responses in the sea pansy Renilla köllikeri take the form of light waves which run over the entire surface of the rachis. As other workers have shown, the responses are controlled by an unpolarized nerve net, and are subject to facilitation. Records obtained by photoelectric techniques are furnished to show certain features of the response. 2. At moderate rates of electrical stimulation (1 per sec.), 2-3 shocks are required to evoke a response. At slower rates, more stimuli are necessary owing to decay of facilitator. At frequencies above 3 per sec., the response rate is slower than the stimulation frequency, owing to refractoriness in the conducting mechanism (c. 0.2 sec.). 3. Summation occurs at frequencies above 1 per sec. This results largely from fusion of the more persistent glowing of autozooids. Siphonozooids are responsible for the brief flashes. 4. Maximal estimates of latent period and flash-duration are of the order of 0.5 and 0.9 sec. respectively. 5. With repeated stimulation, the response intensity is subject to decay. Experiments suggest that this is a consequence of exhaustion of photogenic material. 6. On mechanical stimulation, luminescent waves are evoked at first; but with continued stimulation, refractoriness sets in, and responses become localized to the area of stimulation. Subsequent electrical stimulation reveals that the transmitter mechanism is fatigued, and excitability gradually returns over the course of the next 30-60 mm.