Title MULTIPLE CONDUCTION SYSTEMS AND THE BEHAVIOUR OF SEA ANEMONES Author(s) Mcfarlane, I. D. Citation PUBLICATIONS OF THE SETO MARINE BIOLOGICAL

Electrical activity can be recorded from three distinct conduction systems-the through-conducting nerve net and two slow systems (SSl and SS2). Spontaneous and evoked pulses are shown in recordings from M etridium senile. The responses and interactions of these systems seem to control important components of actinian behaviour. SSI pulses are seen during the opening of Tealiafe!ina in response to dissolved food substances and during shell-climbing in Calliactis parasitica. SSl activity leads to relaxation of oral disk radial muscles in Tealia and to pedal disk detachment in Calliactis. The nerve net and SS2 may control contraction of endodermal muscles in Calliactis. Experimental Analysis of the Behaviour of Sea Anemones Recordings made with extracellular suction electrodes have provided evidence of multiple conduction systems in a number of hydrozoan, scyphozoan and anthozoan species. Research has been concentrated mainly on Hydra, hydromedusae, and colonial hydroids, where recorded pulses are often large, perhaps reaching several millivolts (e.g. PASSANO & McCuLLOUGH, 1963; MACKIE & PASSANO, 1968; JOSEPHSON, 1965). These large pulses may represent activity in non-nervous (neuroid or myoid) conduction systems, but conduction in the absence of nervous elements has been clearly established only in the hydromedusae (see review by MACKIE, 1970). Difficulty often occurs in relating activity of these conduction systems to behavioural events. Some of the large pulses occur spontaneously and appear to accompany activities such as tentacle concerts in Tubularia (JosEPHSON & MACKIE, 1965) and hydranth contraction in Obelia (MoRIN & CooKE, 1971). However, as MACKIE (1968) points out for Cordylophora, pulses may occur in the absence of detectable behavioural events and conversely certain behavioural activities may occur in the absence of recordable electrical events. Similar studies with sea anemones offer certain advantages: 1. The animals are large, solitary and sessile. 2. There is a considerable background of histological, physiological and behavioural knowledge, concentrated mainly on the species Calliactis parasitica, Metridium senile, and Stomphia coccinea. 3. Isolated