A new myxosporean species, Henneguya cynoscioni sp. n., is described from the spotted seatrout, Cynoscion nebulosus (Cuvier) (Sciaenidae) as a causative agent of cardiac henneguyosis. This new myxosporean species is characterized by the morphology of spores and the sequence of SSU rDNA. Examination of 227 spotted seatrout from four South Carolina estuaries in 2008-2010 revealed a 33.5% total prevalence of H. cynoscioni. Henneguya cynoscioni produces lesions in the bulbus arteriosus, its specific site of infection. The severity of lesions and their impact on the bulbus arteriosus is proportional to the number of plasmodial stages developing in this segment of the heart, being most pronounced in host reaction directed against spores liberated from plasmodia.
A new myxosporean species, Kudoa inornata sp. n. (Myxosporea: Multivalvulida), is described from skeletal muscles of the spotted seatrout Cynoscion nebulosus (Cuvier), collected in estuarine waters along the coast of South Carolina, USA. Light microscopic and ultrastructural characters rank this species to the group of Kudoa species with simple-shaped spores. The uniqueness of the SSU and LSU rDNA sequences justifies its status of a new species with sister relationship to Kudoa paniformis. The 100% prevalence in seatrout from four out of five localities sampled and pathogenicity of K. inornata recognized in this study should motivate further screening for infections in its host, which is considered a commercially important game fish with a wide distribution in the Western North Atlantic.