Responses of Cerianthus to Stimulation

Abstract

Cerianthus responds to a single condenser shock by a rapid contraction of tentacles and column. The response is symmetrical no matter where the shock is applied, from aboral end to tentacle tips, is propagated with a velocity of 1–2 m.sec., and is independent of the strength of the stimulus above threshold. The response is followed by an absolute refractory period of 60–70 m.sec. at 22–23° C. and a relative refractory period up to 200 m.sec. after the stimulus. For stimulation of either tentacles or column a threshold at twice the rheobase was obtained by discharge of a 0.05 µF. condenser through a total electrode-plus-preparation resistance of 3,000 ohms, thus giving a capacitance-resistance value of 0.15 m.sec. and chronaxie of 0.05 m.sec. Non-polarizable zinc–sulphate–zinc–agar glass tube electrodes of 0.5 mm. orifice diameter were used. With the same apparatus the chronaxie of the column through-conducting system of Naples specimens of Calliactis was 1.0 m.sec. Hill's¹ equation for the excitation of nerve fits the strength-duration curve for Calliactis but does not approximate closely to that for Cerianthus. Complete curves of the strength-duration relation and the relative refractory period will be published elsewhere.