Digestive capabilities reflect the major food sources in three species of talitrid amphipods

Digestive enzyme activities of three talitrid amphipods were examined to investigate the relationship between their digestive capabilities and diet. Laminarinase, cellobiase, carboxymethyl-cellulase, xylanase, alpha- and beta-glucosidase and lipase were detected in all three species suggesting talitrid amphipods can readily digest dietary carbohydrate and lipid, including complex polysaccharides. Relatively high specific enzyme activity (Units (mg(-1) digestive tract protein)(-1)) of laminarinase and lipase was detected in Talorchestia marmorata, a supralittoral kelp feeder which is coherent with the digestion of lipid-esters and beta-glucans (laminarin) which are the main lipid and storage polysaccharides of brown seaweeds. Talorchestia sp., a low shore intertidal feeder, had high enzymatic activity of alpha- and beta-glucosidase, cellobiase and xylanase, which is consistent with the digestion of diatoms. Keratroides vulgaris, a forest litter feeder had a relatively low specific activity of all enzymes. It is possible that leaf litter is partially digested prior to ingestion by bacteria and fungi present in the rotting vegetation, with bacterial and fungal enzymes contributing to this species' ability to hydrolyse its diet. This study provides the first quantitative data on digestive capacity in these three talitrid amphipods and confirms the relationship between dietary preference and digestive enzyme complement.