Dietary assimilation and the digestive strategy of

Authors: Joanne E Wilde Stuart M Linton Peter Greenaway

Publish Date: 2004/02/04

Volume: 174, Issue: 4, Pages: 299-308

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Abstract

On Christmas Island Indian Ocean the diet of robber crabs Birgus latro Linnaeus was generally high in fat storage polysaccharides or protein and largely comprised fruits seeds nuts and animal material The plant items also contained significant amounts of hemicellulose and cellulose In laboratory feeding trials crabs had similar intakes of dry matter when fed artificial diets high in either fat or storage polysaccharide but intake was lower on a high protein diet Assimilation coefficients of dry matter 69–74 carbon 72–81 nitrogen 76–100 lipid 71–96 and storage polysaccharide 89–99 were high on all three diets B latro also assimilated significant amounts of the chitin ingested in the high protein diet 93 and hemicellulose 496–65 and cellulose 16–53 from the high carbohydrate and high fat diets This is consistent with the presence of chitinase hemicellulase and cellulase enzymes in the digestive tract of B latro The mean retention time 272 h for a dietary particle marker 57Colabelled microspheres was longer than measured in leafeating land crabs The feeding strategy of B latro involves the selection of highly digestible and nutrientrich plant and animal material and retention of the digesta for a period long enough to allow extensive exploitation of storage carbohydrates lipids protein and significant amounts of structural carbohydrates hemicellulose cellulose and chitinWe are grateful to Dr F Stoddard at the Department of Crop Sciences Sydney University for use of the Leco CHN analyser This work was supported by an Australian Research Council grant 942611 PG All experiments complied with Australian and NSW animal ethics legislation

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