Document Type

Honors Thesis

Publication Date



The marine worm Polydora websteri is one of many polychaete species that burrow into the shells of commercially important shellfish. In Maine, local eastern oyster (Crassostrea virginica) farmers are struggling with an infestation of this pest. The worm egests muddy wastes in its burrow causing irritation to the oyster. In response, the oyster secretes new shell material over the burrow forming mud blisters. These blisters are unsightly and decrease the market value of infested oysters, especially for oysters sold in the half-shell trade. In addition to the reduction in market value, the worm may cause physiological stress on the oyster. There have been many studies and anecdotal reports published on possible treatments to eradicate the mudworm. The methods used can be expensive, in some cases toxic, and most are unreliable. I investigated the salinity tolerance of P. websteri using in-situ and in-vitro experiments. The results from both types of experiments can be used to construct improved treatments for infested oysters. I found that P. websteri is not tolerant of extremely low salinities and that a combination of a low salinity exposure followed by a period of dry, cold storage results in 100% worm mortality in as few as 10 days, with minimal host mortality. Future work will focus on scaling up and refining these treatments, as well as looking into possible site-specific management plans for control of P. websteri.