Degradation of mangrove leaf litter by the tropical sesarmid crab Chiromanthes onychophorum

Abstract

In high-diversity tropical mangrove swamps, the relationship between the breakdown to detritus of mangrove plant litter and secondary production of associated estuaries is little understood. This study examined one step in this relationship, the breakdown of mangrove leaf litter to detrital-sized particles by the sesarmid crab Chiromanthes onychophorum, locally very abundant in mangrove swamps of peninsular Malaysia. Contents of the proventriculus (stomach) and of the posterior hindgut, including rectum, were analyzed and particle sizes were measured. Gut contents consisted of more than 95% by volume of mangrove leaf fragments. Particles in the hindgut were of smaller mean size than those in the proventriculus. It is concluded that C. onychophorum consumes fallen leaves or their fragments, incompletely digests them, and returns them to the environment as fecal matter in a more finely-divided state than when they were ingested. C. onychophorum may therefore be a significant agent of mangrove leaf degradation to detrital-sized particles in swamp areas where it is abundant.