Multiple Conduction Systems and the Behaviour of Sea Anemones

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.