TIDAL ACTIVITY RHYTHM OF THE HERMIT CRAB, PAGURUS GEMINUS MCLAUGHLIN

Abstract

Tidal rhythms are known in many animal and plant species living in intertidal zone (Palmer, 1974). One of interesting aspects concerning tidal rhythms is that animals living under the influence of an ordinary change of tide possess tidal rhythms while ones inhabiting shores of a small change of tide do not have rhythms of tidal frequency but of circadian frequency. This has been shown in the relative species of green crabs (Naylor, 1958; 1961), blennies (Gibson, 1965; 1969) and in the same species of fiddler crabs (Barnwell, 1968). The present paper deals with the activity rhythm of the hermit crab, Pagurus geminus, which is one of the commonest inhabitants of Japanese littoral zone and is distributed all over Japan including the Pacific coast with the ordinary change of tide and the japan Sea coast with the small change of tide.