Feeding and resource allocation in the mussel Mytilus edulis: evidence for time-averaged optimization

Abstract

ABSTRACT: Although sustained predominantly by nutrients obtained directly from the environment, metabolic requirements for both gametogenesis and general maintenance in an open-shore population of the bivalve mollusc Mytilus edulis L. from southwest England were also 'subsidized' from substantial energy reserves accumulated during periods of somatic growth. Depletion of these reserves over late winter was associated with a greater sensitivity in the rate of oxidative metabolism to exogenous nutrient availability, diminished metabolic efficiencies with which absorbed ration was utilized, and an associated increase in the instantaneous maintenance requirements. Absorption rates, which were nevertheless minimal during winter, are suggested to be endogenously regulated in a manner more indicative of time-averaged than immediate optimization. It is proposed that such regulation may be especially adaptive within M. edulis, a sedentary species that experiences pronounced annual cycles of food availability, and in which costs deriving from feeding and associated activities are shown to add as much as 38 % to standard metabolic demands.