MYCOBACTERIAL sp. INFECTIONS IN SEA SCALLOPS Placopecten magellanicus FISHED FROM U.S. WATERS IN THE NORTHWEST ATLANTIC

The sea scallop, Placopecten magellanicus, supports an economically important wild fisheries in the northeast U.S.  As part of research to prevent bycatch of yellowtail flounder when fishing sea scallops, sea scallops harvested in the experimental fishing gear trials were shucked and examined.  During this process, researchers identified orange/tan, round to irregularly shaped distinct lesions in tissues of the scallops.  The orange/tan lesions varied greatly in size with the largest being 10 mm in diameter.  The most common location for the nodular lesions was in the smooth adductor muscle.  Nodular lesions were composed of a hemocytic response and consisted of a central caseous core of necrotic debris intermingled with some intact hemocytes (Figure 1a).  This core was circumferentially surrounded by several layers of round to oval to hemocytes then delineated externally by a layer of squamous (flattened) appearing hemocytes.  Abundant bacteria were identified in the caseous core and outer layers of the nodules.  Other smaller nodular lesions were noted in other tissues in severely infected animals.  Histological staining indicated the bacteria were both acid fast (Figure 1b) and Gram positive, thus identifying a Mycobacterial species as the cause of the lesions.  Molecular evaluation of 16S gene from affected tissues strongly suggests a new Mycobacterial species.   Data showing the location and occurrence of the lesions in fished scallops will be presented.  This work was funded by the Sea Scallop Research Set Aside Program (NOAA #NA12NMF4540034 and #NA13NMF4540011) awarded  to the Coonamessett Farm Foundation.