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

Chapter 9: Diseases, Pathogens, and Parasites of the Soft-Shell Clam Mya arenaria

Nicole B. Seitz, Christopher F. Dungan, Charles W. Walker, and S. Anne Boettger


The soft-shell clam Mya arenaria has a pan-global distribution and is an important member of infaunal invertebrate communities along marine and estuarine shores of the northern hemisphere (Cross et al. 2016; Hoffman and Vendrami 2023, this volume). In addition, it has previously been reported as an important bivalve species in northwest Atlantic estuaries from Labrador, Canada through mid-Atlantic USA states (Carlton 2023, this volume), supporting an important commercial fishery throughout much of its range (Kennedy 2023, this volume). Despite numerous historic and current investigations of M. arenaria biology and physiology, reports on its diseases, parasites, and other associates are relatively limited, with dominant recent foci on disseminated neoplasia and Perkinsus sp. infections.

This chapter reviews existing information on a broad range of diseases and parasites of Mya arenaria from the coasts of North America, with a focus on clams from the northwest Atlantic (Table 1). Disease and parasite pathology are subdivided into six major groups: proliferative and infectious diseases, prokaryotic and protist parasites, and metazoan endo- and ectoparasites. Available information is provided on identities and characteristics of disease agents and parasites and on their epizootiologies and impacts. Documented defensive responses of M. arenaria are also described.

Neoplasms are ectopic cell masses or tumors formed due to an uncontrolled and progressive cell proliferation, while neoplasia involves an abnormal proliferation of cells in a tissue or organ resulting in a neoplasm. There are two main neoplasms that develop in bivalves like Mya arenaria—disseminated neoplasia of a diffuse system associated with circulating hemocytes, and a solid tumor or neoplasm associated with the reproductive tissue referred to as gonadal neoplasm.