Natural diet and feeding habits of Thalamita crenata (Decapoda: Portunidae)

Abstract

Thalamita crenata is one of the most common swimming crabs of the mangrove creeks of the East African coast. In Mida Creek, Kenya, this species inhabits the extreme seaward fringe of the mangrove swamp and the intertidal platform in front of the mangal, sheltering in small pools during low tide. Gut content analysis reveals that T. crenata is a generalistic predator, its diet being mainly composed of bivalves and slow moving crustaceans. Both the stomach fullness and the relative presence of animal prey in the contents were significantly higher in crabs collected at sunset than in those caught at dawn. Stomach fullness seems to depend also on the tidal rhythm; in fact, it is higher during spring tide periods. Females had stomachs slightly fuller than those of males, while there was no difference in diet between juveniles and older specimens. Thalamita crenata forages more actively during daytime, thus differing from the majority of swimming crabs. Both the great abundance of this species and its diet, based on a wide range of slow-moving or sessile species, testify to the importance of the role played by this predator in the mangrove ecosystem of Mida Creek.