Activity patterns in Thalamita crenata Portunidae, decapoda): Ashaping by the tidal cycles

Abstract

The activity rhythms of the swimming PortunidThalamitacrenatahave been studied on the basis of crabsightings in surveys along three transects of a mangrove swamp in Kenya. Activity is well matched to theenvironmental regime and is prevalent during the high tides. However, activity does not occur over the wholeof the high tide, but is confined to "temporal windows" corresponding to a water level between 10 and 30 cm.Our findings suggest that activity in Thalamitacrenatais shaped by the tidal cycles and we propose that variationin hydrostatic pressure as the tide changes is the cue which elicits activity.