Sesarmid crabs have important ecological roles in the mangroves of the Indo-west-Pacific biogeographic region. By processing large amount of leaf litter, these crabs retain organic matter in the mangroves, increase the rate of mineralisation, and fuel additional trophic links with the processed material. However, the dietary composition of the mangrove sesarmids is still a controversy. Gut content analyses suggest a dominant contribution of mangrove leaf litter in the crab diet but stable isotope data seem to support the assimilation of organic matter derived from the microphytobenthos but not mangrove litter. In addition, ability of the sesarmid crabs to obtain sufficient nutrition from mangrove litter, which is rich in structural carbon (cellulose) but poor in other nutrients such as nitrogen, has been questioned. The over-arching goal of this thesis was to fill these gaps of knowledge in detritivory of the mangrove sesarmids, using Parasesarma erythodactyla (Hess, 1865), the dominant shredder in sub-tropical Australian mangroves, as an animal model.