Species of the family Reniferidae are trematodes found in the oral cavity and esophagus of snakes from Nearctic and Neotropical regions. Although Renifer heterocoelium has been reported in different snake species from South America, the snails involved in its transmission remain unknown. In this study, a xiphidiocercaria emerged from the physid snail Stenophysa marmorata from Brazil and was subjected to morphological and molecular study. The general morphology, including the shape of the stylet and arrangement of penetration glands, resembles that described for reniferid trematodes from North America. Phylogenetic analysis on the basis of nuclear sequences (28S ribosomal deoxyribonucleic acid gene [1,072 base pairs {bp}] and internal transcribed spacer region [ITS, 1,036 bp]) supports identifying this larva as a member of the family Reniferidae, very possibly a species of the genus Renifer. In the 28S analysis, low molecular divergences were found to Renifer aniarum (1.4%) and Renifer kansensis (0.6%), but also concerning other 2 reniferid species, i.e., Dasymetra nicolli (1.4%) and Lechriorchis tygarti (1.0%). Regarding ITS, the divergences between this Brazilian cercaria and R. aniarum or L. tygarti were 1.9% and 8.5%, respectively. In the case of the mitochondrial marker cytochrome oxidase subunit 1 (797 bp), our Reniferidae gen. sp. differs 8.6–9.6% from Paralechriorchis syntomentera, the only reniferid with sequences available for comparison. We discuss the probable conspecificity of the larval stages here reported with R. heterocoelium, the reniferid species reported in South America.

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