Comparative studies of tidal rhythms. II. The dual clock control of the locomotor rhythms of two decapod crustaceans

The spontaneous locomotory activity of two intertidal crab species was studied in constant conditions. Most of the 57 animals displayed circalunidian rhythms in the laboratory. In 32% of the crabs, the daily scan rates in constant conditions of an individual's two tidal peaks, were different. A dual clock hypothesis is used to explain this response.