Crepidostomum opeongoensis n.sp. (Digenea: Allocreadiidae) from Hexagenia limbata (Serville in Guerin) in Algonquin Park, Ontario, Canada

Abstract

A new species of papillose allocreadiid is described from the abdominal haemocoel of a male nymph of Hexagenia limbata from Lake Opeongo in Algonquin Park, Ontario, Canada. Crepidostomum opeongoensis n.sp. resembles Crepidostomum latum (Pigulewsky, 1931) Hopkins, 1933 and Crepidostomum brevivitellum Hopkins, 1934 in having vitellaria confined to the hindbody, but differs by possessing dorsolateral papillae of the oral sucker that are twice as wide as the dorsomedial papillae. Crepidostomum opeongoensis is further distinguished from C. latum by an oral sucker that is larger rather than smaller than the acetabulum, a body that is twice as large, and a cirrus sac that extends posterior to the acetabulum rather than ending at the midlevel of the acetabulum. It is further distinguished from C. brevivitellum by its longer ventral papillae, greater post-testicular space, and hindbody that widens rather than tapers. The discovery of ovigerous worms of C. opeongoensis in an insect is discussed in relation to other such species in the family.