Seasonal changes in biochemical composition of the bivalve Chlamys septemradiata from the Clyde Sea Area

Abstract

Seasonal changes in the tissue weight and biochemical composition of the pectinid bivalve Chlamys septemradiata (Müller) from a station in the Cumbrae Deep, Clyde Sea Area (UK), were studied during 1969–1971. Separate analyses were made of three divisions of the tissues: the adductor muscle, the gonad, and the remaining tissues referred to as “mantle”. The composition of each of these divisions, and of the total tissues of an animal of standard size was calculated for each sampling date to give information on seasonal changes independent of shell growth. Increase in gonad weight took place mainly between March and May, although there was a slow increase during the winter months (November-March). Spawning in July and August resulted in a fall in gonad weight to very low levels in September and October. The female gonad contained a greater proportion of lipid than the male, and the male a greater proportion of nitrogen than the female, although the total calorific content was similar in both sexes. The adductor muscle showed a clear seasonal cycle of tissue weight and composition, and it was demonstrated that the adductor muscle tissues are a site for storage of reserves. The weight of the adductor muscle was maximal in October-November, and declined through the winter to reach minimum values in March. There was a steady increase during the summer. Lipid, carbohydrate and protein all contributed to the decrease in winter, in part contributing to gonad differentiation but mainly meeting the bivalve's metabolic maintenance requirements. The remaining tissues displayed some irregular fluctuations, but in general the changes showed an upward trend in weight until November followed by a general downward trend to March. The changes are compared with those for other bivalves from the same area.