Associations between parasite burden and health in the spotted seatrout Cynoscion nebulosus
Cosmann, Paul Jerome
de Buron, Isaure
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Spotted seatrout Cynoscion nebulosus are commonly infected by three species of parasites in South Carolina estuaries: the myxosporeans Kudoa inornata (in skeletal muscle) and Henneguya cynoscioni (in the bulbus arteriosus), and the digenean Cardicola laruei (in the ventricle). Because of potentially high pathogenicity by these parasites, we hypothesized that they negatively affect the fishes' health. Burden of infection by each parasite species was quantified in wild-caught spotted seatrout over the course of one year using histology. Fish health was assessed in terms of body and liver masses (measures of energy storage), and spleen mass (a measure of immune response and/or erythropoiesis). Using general linear models to control for the effects of body length, sex, and season, we found that C. laruei was associated with reduced body mass and that K. inornata was associated with reduced liver mass. All three species were associated with changes in spleen mass, with C. laruei being associated with enlarged spleens in all seasons, whereas the effects of K. inornata and H. cynoscioni on spleen mass were season-dependent, with a negative association for K. inornata in the spring and a positive association for H. cynoscioni in the spring. Overall, C. laruei was found to be the parasite that may impact the most the overall health status of the spotted seatrout and H. cynoscioni the least.