Temperature Relationships of the Locomotor Rhythm of Carcinus

The so-called temperature independence of many biological rhythms is of functional importance in maintaining the correct phasing of physiological and behavioural activities despite changes in environmental temperatures. Nevertheless, the rhythms can often be partly modified by changes of temperature and it is necessary to consider the extent of this temperature-dependence when speculating about the possible nature of biological clocks. Perhaps the most striking effects are produced by short periods of exposure to high or low temperatures, though the precise effects of such treatment may vary in different organisms. In some a rhythm may be delayed for the length of period of chilling (Brown & Webb, 1948; Harker, i960; Sweeney & Hastings, 1960), but in others the delay varies according to the precise time of onset of the period of chilling (Stephens, 1957; Biinning, i960; Sweeney & Hastings, i960). The present paper describes a quite different effect of chilling on the locomotor rhythms of Carcinus maenas (L.). It also compares the effects of chilling on the tidal rhythms of Carcinus taken from the shore with the strikingly different effects of chilling on the predominantly nocturnal rhythms of Carcinus from non-tidal docks and of Carcinus from the relatively tideless Mediterranean Sea.