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 parasite’s link in causing changes in sturgeon osmoregulatory capabilities has led us to investigate the host immunophysiology in relation to this host–pa...