The Soft-Shell Clam Mya arenaria: Biology, Fisheries, and Mariculture

Chapter 5: Physiological Ecology of the Soft-Shell Clam Mya arenaria

Matthew W. Gray


Soft-shell clams Mya arenaria inhabit estuaries and bays, which are naturally dynamic and possess rapidly fluctuating environmental conditions. Like many other marine bivalves, M. arenaria is sessile, poikilothermic, and osmoconforming; as a result, its physiological rate functions (e.g., pumping, ingestion, respiration) are often constrained by prevailing environmental conditions. Conversely, these clams have evolved behaviors and physiological processes that quickly respond to environmental factors, enabling them to exploit favorable conditions and avoid some forms of acute stressors such as, respectively, by accelerating feeding rates during when food is plentiful and by performing efficient particle sorting under turbid conditions that dilute diets.

Physiological ecology is the study of how an organism’s physiological processes respond to biotic and abiotic environmental conditions. Ecophysiological studies are used to understand the environmental limits of soft-shell clams to help explain their distribution, trophic interactions, production, and other ecosystem effects. These studies also help understand the adaptation potential of M. arenaria in the face of anthropogenic alteration to their habitat.

Although numerous physiological rates respond to environmental conditions, some of the most important for sessile aquatic invertebrates are those associated with processing suspended particles for ingestion. Therefore, this chapter mainly focuses on the anatomy, physiology, and behaviors of M. arenaria associated with water pumping, particle processing/suspension feeding, and accessing the water column (see Table 1 for definition of terms used throughout the chapter). Such features and functions are also discussed in the context of M. arenaria’s ability to contend with the dynamic conditions found in estuaries. The work synthesizes much of the existing literature on feeding physiology for M. arenaria and, when information gaps are encountered, includes results from studies of other clam and epifaunal bivalve species. The habitats discussed in this chapter include numerous bays and estuaries with varying levels of salinity, temperature, and eutrophication. The spatial distribution of populations referred to herein ranges from subarctic to subtropical regions that span several seas in the Northern Hemisphere. The chapter concludes with recommendations for future research to clarify how the physiology of M. arenaria responds to an array of current and future estuarine environmental conditions.