Mud Blister Worms and Oyster Aquaculture

The mud blister worm, Polydora websteri Hartman (Loosanoff and Engle 1943), burrows into the shells of bivalve mollusks, including Eastern oysters (Crassostrea virginica), sea scallops (Placopecten magellanicus) and blue mussels (Mytilus edulis). 

The mud blister worm, a marine polychaete, lives worldwide and is distributed throughout the estuarine waters of Maine and the northeastern U.S., and has been found in the shells of other mollusks common to the region (Blake 1971). The earliest descriptions of Polydoradate back to the 1890s (Whitlegge 1890) and early 1900s. More recently, attention on this species has focused on damage to stocks of oysters in Australia and along the U.S. Atlantic and Gulf Coasts, attributed to the growth of the half-shell market for oysters, and in the negative reaction by some markets toward product that exhibits blister worm infestation. While some markets have remained strong for oysters with some level of infestation, producers report buyer responses that range from reduced demand, to reduced farm-gate prices, to outright rejection of the product. 

This report is for oyster producers interested in controlling mud blister worms, which when present in large numbers can reduce the value of oysters sold to the half-shell market. Although other species of blister-causing worms occur in several genera including Polydora, Pseudopolydora,and Boccardia, this report focuses specifically on Polydora websteri.