Opercular lesion in wild black drum, Pogonias cromis (Linnaeus, 1766), associated with attachment of the sea louse Sciaenophilus tenuis (Copepoda: Siphonostomatoida: Caligidae)

Sea lice, Sciaenophilus tenuis (Copepoda: Caligidae) are important pathogens in aquaculture, and because more fish species are being intensively cultured, more species of sea lice are recognized as pathogens. The present American study was to gather baseline data regarding the effects of sea lice on a valuable sciaenid (Sciaenidae), the black drum, Pogonias cromis, by describing lesions associated with naturally occurring infections of Sciaenophilus tenuis van Beneden, 1855. Gross and histological examinations of copepods and lesions were made using light and scanning electron microscopy from samples collected from eight infected black drum captured in Mississippi Sound, northern Gulf of Mexico. Adult females of S. tenuis were associated with a mucosal lesion on interopercula. Female copepods attached to folds of mucosa on the posterior half of interopercula with cephalothoraces directed anteriorly in parallel with the longitudinal axis of fish. All attached male copepods grasped the abdomen or genital complex of females and were not in contact with the host. Maxillipeds of female copepods were embedded in epithelium or subepithelial connective tissue and functioned as the primary attachment appendages. Epithelial hyperplasia, fibrosis of subepithelial connective tissue, and chronic inflammatory infiltrates including presumed eosinophilic granular cells surrounded maxillipeds, indicative of long-term, focal, parasite-host interaction. Aquaculture managers should regard S. tenuis as a potentially serious pathogen if fish develop intense S. tenuis infections associated with extensive gross lesions.