ELECTRICAL ACTIVITIES OF THE ANTHOMEDUSAN, SPIROCODON SALTATRIX (TILESIUS)

¹ Tamano Marine Laboratory, 2-3-3, Shibukawa, Tamano, Okayama, 706 Japan

1. Electrical activities occurring spontaneously and in response to electrical or photic stimulation were recorded from nervous, muscular and non-nervous tissues of Spirocodon saltatrix.

2. Two types of quick pulses, nMP's and PSP's, were recorded from the nerve ring. nMP's originated in the outer nerve ring and PSP's, in both the outer and the inner nerve rings. The PSP's appeared to trigger swimming contractions because they always preceded the muscle contraction pulses of the bell (SSP's) and the velum(VSP's).

3. Composite pulses with quick and slow phases (QSCP's) and slow monophasic pulses (SMP's) were recorded on the subtentacular region and the tentacles, respectively. The QSCP's had an intimate relationship with nMP's and their quick components appeared to be of nervous origin as were nMP's and PSP's. The SMP's seemed to be myonal or epithelial events and their conduction was restricted to each radial streak.

4. Contraction pulses of the velum (VSP's) and the subumbrellar muscle (SSP's) consisted of two phases and a steady phase between the two. The electrogenic site of the first phase was discussed from the results of polarity reversal when the positions of the recording and the indifferent electrodes were reversed.

5. Pulses (EDP's and EP's) also occurred in response to electrical stimulation on the exumbrellar surface and the subumbrellar endodermal lamella, respectively.

6. All types of pulses except the EDP's and EP's occurred upon light-off but none of them responded to light-on. Though the information of light-off was considered to originate in each ocellus, no electrical correlate as regards the information carrier has been observed.

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