Evidence of endogenous circadian and ultradian activity rhythms of talitrids from different environments

Previous studies on amphipod biological rhythms show differences in behaviour between and within species and populations. In five populations, involving three species of talitrids from different habitats in the Maremma Regional Park (Grosseto, Italy), nocturnal circadian, bi-modal and arrhythmic animals were found. This behavioural variation can be explained by the necessity of adapting to the characteristics of the different habitats in which the animals are found. A comparison of these data with those reported in the literature and a further case study of animals from an Atlantic coast reveals differences in the expression of bi-modal rhythms in Mediterranean talitrids with respect to samples from Oceanic coasts.