Circatidal Rhythms and Their Entrainment to the Tidal Cycle in Insects

Abstract

Some intertidal insects show endogenous activity rhythms that synchronize with the tidal cycle, that is, circatidal rhythms. In this chapter, we collected studies of the circatidal activity rhythms of intertidal insects and the entrainment of the circatidal rhythm to the tidal cycle. Until now, circatidal activity rhythms have been reported in three taxonomic groups: springtails (Collembola), beetles (Coleoptera), and crickets (Orthoptera). The mangrove cricket Apteronemobius asahinai is known as the only insect species that shows clear and persistent circatidal activity rhythms. When the inundation cycle with a period of 12.4 h was provided by artificial means, the circatidal rhythm of A. asahinai responded to the given periodic inundations in a phase-dependent manner. Furthermore, the molecular mechanism of the circatidal clock of A. asahinai is likely to be different from the circadian clock. Advances in studies in A. asahinai will lead to better understanding of the circatidal rhythm in insects.