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Journal of Experimental Biology 58,463-471 (1973)
Published by Company of Biologists 1973

Properties of Stalk-‘Muscle’ Contractions of Carchesium SP

M. RAHAT ¹, Y. PRI-PAZ ¹, and I. PARNAS ¹

¹ Department of Zoology, The Hebrew University of Jerusalem, Israel

1. The stalk of Carchesium was found to contract in an ‘all or none’ fashion in response to electrical stimuli. Rise time and half-decay time of contractions were 40-60 msec and 800-900 msec respectively.

2. Forces developed during contraction were between 400-800 g/cm².

3. At 0.2 stimuli/sec or less, the stalk contracted at a one-to-one ratio. At higher rates of stimuli the stalk contracted at its own pace, indicating an intrinsic refractory system.

4. No tetanic responses or summation were observed in normal stalks. In fatigued stalks, partial summation was obtained and relaxation time was increased.

5. It is concluded that the contractile system of Carchesium is probably different from that of a metazoan muscle.