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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03675

    Black eye syndrome and a systemic Rickettsia-like organism in Alaskan Chionoecetes spp. crabs, including normal eyestalk microanatomy

    Theodore R. Meyers*, Richard Morris, Tyler M. Jackson, Julia N. Dissen, Laura M. Slater, Maya L. Groner

    *Corresponding author:

    ABSTRACT: A black eye syndrome (BES) was discovered in both captive and wild populations of Alaskan snow Chionoecetes opilio and Tanner C. bairdi crabs. Field prevalences ranged from 0.37% (n = 594/161295) to 19.6% (n = 62/316) in snow crabs from the eastern Bering Sea and 0.09 (n = 15/16638) to 0.7% (n = 133/18473) in Tanner crabs from the same trawl samples with a slightly greater percentage (1.4%, n = 57/3945) in Tanner crabs from the Aleutian and Kodiak Islands fisheries in the Gulf of Alaska. BES is not associated with crab mortality and has 2 distinct manifestations: abnormal black foci of internal eye pigment with no discernable histological lesions which, in many cases, is followed by corneal shell disease with ulceration and distal eyestalk erosion. It is assumed for this study that these are early and late stages of BES that are somehow related. Our results suggest that early stages of abnormal pigmentation are noninfectious, possibly related to changing ocean conditions affecting crab endocrinology and neuropeptide control of secondary eye pigment. Potential light induced photoreceptor damage of harvested crabs with dark-adapted eyes is another anthropogenic factor possibly contributing to the early changes in eye pigmentation. Normal eyestalk microanatomy specific for Chionoecetes spp. is provided as necessary baseline information for future studies. Early in the study an unreported rickettsia-like organism (RLO) was discovered infecting dissected black eyestalks submitted for examination from 5 of 6 dead snow crabs suggesting association with BES. Subsequent samples indicated the RLO was systemic, infected both black and normal appearing eyestalks and was unrelated to BES. However, the multi-organ infection and histopathology indicated the RLO could be a primary pathogen of snow crabs.