Molecular and morphological characterisation of flatworm larvae parasitising on fish in Cat Tien National Park, Vietnam

Abstract

Cat Tien National Park in southern Vietnam provides a unique opportunity to study the diversity of parasites associated with animals of the plains of tropical forests and lowland river basins in Southeast Asia. In this study we provide morphological description and phylogenetic analysis based on partial sequences of the 28S rRNA gene of metacercariae belonging to five species: Clinostomum sp., Posthodiplostomum sp. 1, Posthodiplostomum sp. 2, Crassiphialinae gen. sp. 1 and Crassiphialinae gen. sp. 2, collected in four species of freshwater fish (Rasbora paviana, Trichopodus trichopterus, Anabas testudineus and Channa striata). The digenean Clinostomum sp. was found to be phylogenetically close (possibly conspecific) to metacercaria of Clinostomum sp. recorded in Australia. There are no sequences in the GenBank database identical to any Posthodiplostomum spp. nor two other crassiphialine metacercariae found by us. Phylogenetic analysis supports the sister position of Crassiphialinae gen. sp. 1 to the Uvulifer spp. + Crassiphiala spp. group of crassiphialine trematodes. At the same time, phylogenetic relationships of Crassiphialinae gen. sp. 2 were poorly resolved. We also provide morphological description, cox1 and 28S rRNA genes-based reconstruction of phylogeny for the plerocercoid of solenophorid cestode Scyphocephalus sp. ex liver of Trichopodus trichopterus. Phylogenetic analyses unite plerocercoid of Scyphocephalus sp. in one group with solenophorid Duthiersia expansa, while the type species of the genus Scyphocephalus – S. bisulcatus– appears as a sister to Duthiersia fimbriata on the tree. Thus, phylogenetic data cast doubt on both the monotypy and the monophyly of the genus Scyphocephalus. This is the second record of plerocercoids of solenophorids and the first one of fish as second intermediate host of this cestode family.

Keywords

• clinostomum
• crassiphialinae
• fresh waters
• metacercariae
• plerocercoids
• posthodiplostomum
• scyphocephalus
• tropics