Lesions associated with plerocerci (Platyhelminthes: Cestoda: Trypanorhyncha) in the gastric wall of a cownose ray, Rhinoptera bonasus (Mitchill), (Myliobatiformes: Rhinopteridae) from the northern Gulf of Mexico.

We describe lesions associated with a seemingly intense infection of trypanorhynch plerocerci (Platyhelminthes: Cestoda: Trypanorhyncha) in the gastric wall of a female cownose ray, Rhinoptera bonasus (Myliobatiformes: Rhinopteridae) captured in the northern Gulf of Mexico. Grossly, the multitude of encapsulated, encysted plerocerci imparted a bumpy and cobbled appearance to the serosa of the stomach, and none was observed in any other tissue during routine parasitological necropsy. Histologically, the plerocerci were associated with severe intramural granulomatous gastritis, vascular ectasia and mesothelial polyposis with the exclusion of the mucosa. To our knowledge, this is the first published case study documenting platyhelminth-associated histopathological changes in the gastrointestinal tract of R. bonasus as well as that of the efficacy of immunocytochemical markers for smooth muscle actin, Factor VIII, S-100, and proliferating cell nuclear antigen in Myliobatiformes. It also may serve as a potential primer for much needed ecological investigations regarding the potential role of elasmobranchs as intermediate or 'paratenic' hosts in the life cycles of trypanorhynch cestodes.