A Combined Morphometric and Molecular Approach to Identifying Metacercariae of Euclinostomum heterostomum (Digenea: Clinostomidae)

Metacercariae of species of Euclinostomum have been found encysted in kidney, liver, and muscles of several fish species, while adults occur in the mouth, pharynx, larynx, trachea, and upper esophagus of fish-eating birds. The aim of this work was to gather molecular and morphological data from the type species, Euclinostomum heterostomum, as a starting point for needed revisions of the genus. Metacercariae were collected from cichlids in Lake Kinneret, Israel, and all were identified as E. heterostomum based on morphology. This identification was further confirmed by principal components analyses that revealed no partitions in morphometric resemblance, indicating that the material represents a single species, and that the specimens were morphometrically similar to other descriptions of E. heterostomum. In phylogenetic analysis of concatenated partial internal transcribed spacer 1 and 2, 5.8S rDNA, and partial cytochrome c oxidase I barcode sequences, the isolates of Euclinostomum obtained in this study form a single, monophyletic group separate from recently published data from Euclinostomum sp. from Thailand and from Clinostomum species, which are also monophyletic. The morphological and molecular data reported in the present work can provide a useful point of reference for future studies.