Seasonal changes in the digestive enzyme levels of the amphipod Corophium volutator (Pallas) in relation to diet

The diet of the amphipod Corophium volutator (Pallas) living on extensive intertidal mud flats in the Bay of Fundy, eastern Canada, was investigated by direct and indirect methods. Microscopic observation of gut contents revealed macrophyte detritus but few diatom frustules. Laboratory cultures showed good survival on a diet of benthic diatoms, while on a diet of Spartina detritus survival was poor, although significantly better than the survival of starved animals. The ratios of gut enzyme activities, amylase to protease and amylase to laminarinase, changed markedly with the season. In summer the ratio was similar to that of animals cultured on a diet of benthic diatoms; in spring it resembled that of animals cultured on Spartina detritus, while in winter it was similar to that of starved animals. It is concluded that in summer, rapid growth is made possible by feeding on benthic diatoms, while Spartina detritus is an inferior food source which aids survival at other times of the year.