Growth uncoupling and the relationship between shell growth and metabolism in the soft shell clam Mya arenaria

Abstract

The goal of this study was to investigate whether shell growth reflects metabolic rate rather than overall or somatic tissue production in the soft shell clam Mya arenarja. This was accomplished by conducting laboratory experiments exposing clams to different levels of food, immersion period and temperature in order to uncouple shell and soft tissue growth, and then determining if shell growth and oxygen consumption remained positively correlated. Soft shell clams were raised in a simulated intertidal system for 2 to 3 w k to acclimate them to experimental conditions. After acclimation. oxygen consumption, a measure of metabolic activity, ingestion rate, a measure of energy intake, shell growth and soft tissue growth were estimated for all individuals. Tissue and shell growth were successfully uncoupled in all experiments In the 2 expenments where significant changes in shell growth, soft tissue growth and oxygen consumption occurred, shell growth was posit~vely correlated to oxygen consumption. Soft tissue growth was either uncorrelated or negatively correlated to oxygen consumption and shell growth. Shell transparency In thin sections increased with metabolic rate, while shell growth line clarity decreased in those treatments most stressful to the clams (i.e. low food level a n d high temperature). Our results are cons~stent with the hypothesis that shell growth is coupled to metabolic activ~ty and IS not a measure of somatic tissue production We suggest that information on physiological rate processes is recorded in the shell of b~valves, and that growth line patterns may be used to reconstruct metabolic rates from field collected individuals