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Cuticular lesions from twenty-four market sized lobsters (Homarus americanus) with winter impoundment shell disease were examined. Histological descriptions of cuticular lesions were correlated with the substage of molt for each lobster, because cuticle components and inflammatory mechanisms vary in each. A lesion severity grading system was developed and applied to four specific substages of the five-stage (A-E) molting cycle. Lesions present in substage C4, in which the membranous layer is deposited, and D0 (passive premolt) were divided into five grades, ranging from mild erosions (Grade I) to severe ulceration (Grade V) of the cuticle. Cuticular lesions from lobsters in C4/D0 were compared with cuticular lesions from lobsters in substages C2/C3. Defensive mechanisms exhibited by animals in all substages were epicuticle deposition, melanization, inflammatory cell infiltration, and pseudomembrane formation. In addition, animals in C4 and D0 showed proliferation of the membranous layer in affected foci. The lesion grading scheme presented in this paper can be used to describe and compare both inter- and intraspecies crustacean shell lesions.

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We evaluated marine aggregates as environmental reservoirs for a thraustochytrid pathogen, Quahog Parasite Unknown (QPX), of the northern quahog or hard clam, Mercenaria mercenaria. Positive results from in situ hybridization and denaturing gradient gel electrophoresis confirm the presence of QPX in marine aggregates collected from coastal embayments in Cape Cod, Massachusetts, where QPX outbreaks have occurred. In laboratory experiments, aggregates were observed and recorded by entering a quahog's pallial cavity, thereby delivering embedded particles from the water column to its benthic bivalve host. The occurrence of pathogen-laden aggregates in coastal areas experiencing repeated disease outbreaks suggests a means for the spread and survival of pathogens between epidemics and provides a specific target for environmental monitoring of those pathogens.

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