New amphistome (Trematoda) genera and species from Amazonian serrasalmid fishes, Myleus (Myloplus)

Abstract

Two new genera and three new species of amphistome trematodes (Cladorchiidae) are described from Amazonian serrasalmid fish. These species appear to be characteristically found in the subgenus Myleus (Myloplus) since they are nearly always found together in the three species in this subgenus (rubripinnis, asterias and an undescribed species). They have not been found in four other species of Myleus caught in the same localities. The new genera and species are: Inpamphistoma papillatum gen. et sp. n., Annelamphistoma elegans gen. et sp. n. and Dadayius pacuensis sp. n. The two new genera have ventral surfaces that are convex and covered with papillae which would appear to separate them from all other known genera among the amphistomes. They differ from each other by body shape and the number of muscular puckers in the body wall. Inpamphistoma is flattened, strongly concave dorsally and has one pair of muscular puckers. Annelamphistoma, on the other hand, is only slightly concave dorsally and is provided with five pairs of puckers. SEM studies showed that the ventral papillae are domed to conical and are neither cililated nor branched. Additionally, circles of domed papillae with pores are found around the mouth of Inpamphistoma. Dadayius pacuensis sp. nov. has the transverse tegumental folds in the botto mof the acetabular cavity that characterize the genus. The new species has a massive acelabulum which serves to distinguish it from the type and only species. It also differs from the type in being only one-half as large. The three amphistomes described here were found together in nearly every adult specimen of fish belonging to Myleus (Myloplus) and are as widely distributed geographically as their hosts.