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 activities of the main digestive organs (crystalline style and digestive gland) of the cockle Cerastoderma edule have been investigated. The simultaneous increment of specific enzyme activities (mg end product/mg protein per h), mass (mg), and protein content of digestive organs yield a remarkable enhancement of total enzyme activities (mg end product per organ/h) during Spring-Summer as compared with Autumn-Winter. Although extracellular enzymes of the crystalline style have typically received more attention than intracellular enzymes from the digestive gland, the present study shows the latter to release as much as ten times higher total activities than the crystalline style, highlighting the relevance of intracellular digestion in cockles. The sole effect of temperature on enzyme activity does not explain recorded seasonal variability. Additionally, the present study has shown that enzyme activities 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 shaping of the seasonal cycles may be influenced by requirements of specific biochemical components and past feeding history. (C) 1998 Elsevier Science Inc. All rights reserved.