Entrainability by salinity cycles of rhythmic locomotor activity in normal and eyestalk ablatedcarcinus maenas(L).

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Abstract
The temporal patterns of spontaneous locomotor activity were compared in normal and eyestalk ablated crabs. Study of entrainment of such patterns to simulate tidal cycles of salinity change entails separation of the exogenous responses to low salinity and endogenous circatidal rhythmicity which is re‐phased by episodes of normal ambient salinity. A method to transform rhythmic data to emphasise separate rhythmic patterns of behaviour was therefore developed, and patterns of re‐entrainment to ambient salinity cues were established. Having established the normal pattern of entrainment, experiments were then carried out on eyestalk‐ablated crabs. In such animals it was found that the exogenous responses to low salinity episodes of imposed salinity cycles were not affected but the entrainment responses to ambient salinity episodes were lost. In addition, eyestalkless crabs, unlike controls, showed no evidence of free‐running endogenous rhythmicity after entrainment in a salinity cycle.