First integrative assessment of Ochetosoma heterocoelium (Travassos, 1921) (Digenea: Ochetosomatidae) parasite of Bothrops moojeni Hoge, 1966 (Reptilia: Viperidae) from Brazil.

Ochetosoma heterocoelium (Travassos, 1921) was collected from the mouth and oesophagus of a pit viper, Bothrops moojeni Hoge, 1966 in São Sebastião do Paraíso Farm (21°51'48.26" S, 48°26'56.78" W), municipality of Boa Esperança do Sul, São Paulo State, Brazil. In this study, we provide the first molecular characterisation of this digenean using 28S rDNA and COI sequences, and its phylogenetic position within the Plagiorchiida is assessed. Furthermore, new morphological features are added to the diagnosis of the species, and scanning electron microscopy photomicrographs are presented. Sequences of the 28S rRNA gene of O. heterocoelium were successfully obtained and aligned with 35 digenean species belonging to Plagiorchiida. Only three congeners - O. aniarum (Leidy, 1890), O elongatum (Seo et al. 2024), and O. kansense (Crow, 1913) - have been sequenced for this molecular marker. The newly sequenced individuals of O. heterocoelium are 98.7% and 99.4% similar to O. aniarum and O. kansensis, respectively, and Ochetosoma is not recovered as a monophyletic group. Dasymetra nicolli Holl and Allison, 1935 and Lechriorchis tygarti Talbot, 1933 are nested with Ochetosoma.