SEASONAL-VARIATION OF DIGESTIVE ENZYME-ACTIVITIES IN THE DIGESTIVE GLAND AND THE CRYSTALLINE STYLE OF THE COMMON COCKLE CERASTODERMA-EDULE

Seasonal variation of amylase, cellulase, laminarinase and protease ac tivities of the main digestive organs (crystalline style and digestive gland) of the cockle Cerastoderma edule have been investigated. The s imultaneous increment of specific enzyme activities (mg end product/mg protein per h), mass (mg), and protein content of digestive organs yi eld a remarkable enhancement of total enzyme activities (mg end produc t per organ/h) during Spring-Summer as compared with Autumn-Winter. Al though extracellular enzymes of the crystalline style have typically r eceived more attention than intracellular enzymes from the digestive g land, the present study shows the latter to release as much as ten tim es higher total activities than the crystalline style, highlighting th e relevance of intracellular digestion in cockles. The sole effect of temperature on enzyme activity does not explain recorded seasonal vari ability. Additionally, the present study has shown that enzyme activit ies in the digestive gland increased rapidly (3 days) in the presence of food at any time of the year, suggesting that seasonal variation of enzyme activities would reflect a process of continuous adjustment of digestive enzyme levels to environmental food availability. Further s haping of the seasonal cycles may be influenced by requirements of spe cific biochemical components and past feeding history. (C) 1998 Elsevi er Science Inc. All rights reserved.