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Hard Clam Neoplasia

Identification of the cause of hemic neoplasia in Mercenaria mercenaria and development of management methods

Since 2009 a new disease in hard clams that appears similar to disseminated neoplasia that has been documented in other bivalves has been monitored in Wellfleet Harbor, MA. It has spread from just a few locations (highest in specific locations in Wellfleet harbor) to most of the hard clam aquaculture plots in town waters. This neoplastic disease is composed of circulating abnormal cells in the hemolymph. In early infections the neoplastic cells are noted in low abundance throughout the vessels of the clam. As the disease progresses within an animal, fewer and fewer normal hemocytes are noted and eventually the sinusoids and vessels are filled and visibly “plugged” by the proliferating neoplastic cells causing death. Ramifications of this disease to the entire industry could be significant.  Right now it appears to be a localized problem, but without directed research to understand the epidemiology there are few to no recommendations for “on the farm” management of this disease.

In this project we will 1) identify the mode of transmission of the disease; 2) examine the extent of the disease in Wellfleet in 2018 and 2019 and in year two by sampling water and sediment for neoplastic cells; 3) identify the origin of the neoplastic cells and determine whether a retro-element is involved in the transformation; and 4) develop a quantitative PCR test method for the disease to be used in this research on hemolymph samples, water and sediment and for ultimate use for disease diagnosis in a diagnostic lab.

Funding Agencies

The USDA Northeast Regional Aquaculture Center funded this research.


This is a collaboration led by Dr. Roxanne Smolowitz (Roger Williams University) with Gast at WHOI and Diane Murphy (Cape Cod Cooperative Extension & Woods Hole Sea Grant).