A New Species of Caudotestis (Digenea: Opecoelidae) Parasitizing the Horsefish, Congiopodus peruvianus (Scorpaeniformes: Congiopodidae) from the Patagonian Shelf, Argentina

Abstract: A new species of digenean, Caudotestis patagonensis n. sp. (Digenea: Opecoelidae), is described and illustrated based on specimens collected from the intestine of the horsefish, Congiopodus peruvianus (Cuvier, 1829) (Scorpaeniformes: Congiopodidae) from the Patagonian Shelf, Argentina (45–48°S, 60–64°W). This opecelid differs from the 4 previously known species of Caudotestis mainly in the extent of its seminal vesicle within the hindbody and the distribution of vitelline follicles. Moreover, the new species can also be distinguished by possessing the following combination of features: oral and ventral suckers nearly equal in size, ventral sucker at boundary of anterior third of body, intestinal bifurcation in posterior third of forebody and anterior to genital pore, genital pore submedial sinistral, anteriormost extent of the excretory vesicle reaching ovarian region, ovary nearly equidistant from both ventral sucker and anterior testis, posteriormost extent of the uterine loops just reaching o...