Immunophysiology of Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus (Mitchill), and the relationship to parasitic copepod, Dichelesthium oblongum (Abilgaard) infection

The copepod parasite, Dichelesthium oblongum, is known to infect the Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus, within the area near New York city, USA, known as the NY Bight. The gross pathology associated with the juvenile and adult copepod stages along with the parasites link in causing changes in sturgeon osmoregulatory capabilities has led us to investigate the host immunophysiology in relation to this hostparasite system. All the host variables, which included gill Na+-K+-ATPase activity, serum alkaline phosphatase (AP) and white blood cell differential counts, were affected in a non-linear manner by the copepod parasite. The parasites increased the host gill Na+-K+-ATPase activity and serum AP along with the percentage granulocytes while decreasing the percentage lymphocytes. A new method, developed to sample and preserve white blood cells in the field for future flow cytometry analysis, proved adequate. The effects of fish size, location and time of sampling were accounted for by the use of generalized linear models, and their effects on the host variables are discussed.