Circa-tidal Pacemakers in the Nervous System of an Amphipod

Abstract

Control centres for endogenous rhythms of circadian frequency have been located in the pineal gland and in the supra-chiasmatic nucleus of vertebrates (e.g. see this volume), and analagous structures have been identified in the nervous system of invertebrates (see review by Page, 1981). In contrast oscillators controlling the circa-tidal rhythms shown by so many intertidal animals have yet to be located. Naylor and Williams (1968) rephased the tidal activity rhythms of the shore crab Carcinus by chilling the eye stalks alone, thus implicating the x organ/sinus gland complex, but endogenous circatidal periodicity has also been demonstrated in the swimming activity of many sessile eyed crustaceans. The location and nature of the mechanism controlling the rhythmic swimming of one such animal, the estuarine amphipod Corophium volutator is the subject of the present communication.