Seasonal partitioning and utilization of energy reserves in two age classes of the bay scallop Argopecten irradians irradians (Lamarck)

Abstract

Seasonal cycles in body component indices, reproductive condition (determined histologically), and storage and utilization of protein, lipid and carbohydrate reserves in various tissue pools, were investigated in two cohorts of the bay scallop Argopecten irradians irradians (Lamarck). Scallops were held in cages at two contrasting localities in Long Island, New York, U.S.A. Gametogenesis occurred mainly at the expense of adductor muscle protein and lipid reserves. Energy loss in the adductor muscle could potentially account for 63 to 99% of the gonadal buildup in the spring. In contrast to prior studies, digestive gland lipid and muscle carbohydrate made an insignificant contribution to the energy demand during reproduction. In first-year, pre-reproductive scallops, adductor muscle protein also contributed 63–66% of the total energy loss during overwintering stress. Senescence of older scallops was evidenced by a more rapid decline in mantle protein reserves than in young individuals. Twenty percent of the older population showed signs of anomalous, advanced oogenesis in March, coincident with the period of highest natural mortality. Results of this study suggest a possible association between senescence and protein metabolism. Contrary to studies showing glycogen to be the main storage product in bivalves such as oysters and mytilids, this study serves to stress the importance of protein as an energy substrate in pectinids.