The digestion of cellulose and other dietary components, and pH of the gut in the amphipod Gammarus pulex (L.)

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Abstract
SUMMARY. Gut extracts from Gammarus pulex hydrolysed native and other cellulose substrates in vitro. Digestive fluid cellulase is probably endogenous as cell‐free fluid mediated cellulose hydrolysis, but no bacteria were isolated from the fluid which produced a detectable extra‐cellular cellulase. There was no apparent digestion of plant cell walls during their passage along the digestive tract, which took about 5–7 h at 10°C. The pH sensitivities of the digestive enzymes and the pH of the various regions of the gut suggest that carbohydrate digestion occurs in the proventriculus, midgut glands and anterior midgut, but protein digestion may be largely limited to the posterior midgut. The pH of the digestive fluid was altered slightly, but significantly, by the consumption of different natural and artificial test diets and by starvation. The most probable reason for the non‐digestion of plant cell‐walls is the lack of necessary enzymes other than cellulase. The role of cellulase may be confined to digesting the many small, non‐cellular particles which are present in the gut.