Redescription of Crepidostomum opeongoensis Caira, 1985 (Trematoda: Allocreadiidae) from fish hosts Hiodon alosoides and Hiodon tergisus (Osteichthyes: Hiodontidae).

Crepidostomum opeongoensis Caira, 1985 (Trematoda: Allocreadiidae) is redescribed from fish hosts Hiodon alosoides and Hiodon tergisus in southern Manitoba. The redescription adds details regarding the surface morphology and reproductive structures of the parasite not described previously. These include the characteristic tegumental papillae around the oral opening, paired papillae on the ventral and dorsal surfaces of the body, and tegumental bosses on the dorsal surface of the forebody. Crepidostomum opeongoensis co-occurred with its hypothesized sister species. Crepidostomum illinoiense, in all host individuals harboring the former, and both species are characteristic of hiodontids. The association of C. opeongoensis with hiodontids and the absence of hiodontids in Lake Opeongo where C. opeongoensis was originally reported indicate that the Algonquin Park region may have had hiodontids in the past and that the life cycle may be completed at present without the original fish host.