Timing of locomotor activity in the New Zealand rock lobster,Jasus edwardsii

Abstract

Abstract Laboratory studies of the locomotor activity of individual rock lobsters (Jasus edwardsii) were made in a 24 h light/dark cycle (LD) and in constant dim red light. The majority of animals studied in a normal LD cycle exhibited nocturnal activity patterns. Levels of illumination as low as c. 0.03 μE nrV1 were usually sufficient to suppress activity during the light phase. If the duration of the dark phase was normal for the time of year, the majority of animals became active at the beginning of the dark period and remained active until its end. Thus in winter, animals were active for 13–14 h each day whereas in summer theaetive period was curtailed to 8–9 h. In summer, animals held in a LD cycle with 13–14 h of darkness did not increase the length of their active periods to match the dark phase. The involvement of an endogenous timing system in this species is indicated, although its control is not rigid and in the majority of animals studied it appears to be completely overridden. The weak intern...