Morphological and molecular characterization of Haplorchoides mehrai Pande and Shukla 1976 (Digenea: Heterophyidae) from Chiang Mai province

Cyprinoid fish in Chiang Mai province has been reported the presence of a large number of metacercariae, particularly the metacercariae of Haplorchoides and those not identified to species. This study aims to investigate morphological and molecular characteristic of the minute intestinal fluke H. mehrai metacercariae in two cyprinoid fish species from Chom Thong district, Chiang Mai province, Thailand: the Tinfoil barb (Barbonymus schwanenfeldii) and the White eye barb (Cyclocheilichthys repasson). A total of 180 fish (90 from B. schwanenfeldii and 90 from C. repasson) were collected over three seasons: cool, hot and the rainy season (December 2015 to August 2016). Fish were examined for H. mehrai metacercariae infection, including areas such as muscle and the inner side of body scales, by using a light microscope. The prevalence of H. mehrai metacercariae in B. schwanenfeldii and C. repasson was 73.33 % and 100 % respectively. Haplorchoides metacercariae were identified as H. mehrai based on the morphological characteristics; the position of the acetabulum and the number and arrangement of the acetabular spines. Phylogenetic analysis based on Cytochrome c Oxidase subunit I (COI) gene showed that H. mehrai metacercariae from B. schwanenfeldii and C. repasson were the same species as the adult stage of H. mehrai from Hemibagrus nemurus and Mystus multiradiatus. Both morphological and molecular characteristic could indicate that Haplorchoides metacercariae originated from this study were H. mehrai. Furthermore, it is a new record of the minute intestinal fluke Haplorchoides mehrai in Chiang Mai Province