The life cycle of Asymphylodora perccotti sp. n. (Trematoda: Lissorchiidae) in the Russian Southern Far East.

Specimens of Asymphylodora perccotti sp. n. (Trematoda: Lissorchidae) were found in the esophagus of the freshwater fish Perccottus glenii (Odobantidae) taken from the Bolshaya Ussurka River Basin (Primorsky Region, Russian Southern Far East). The first intermediate host of this trematode is a gastropod, Parafossarulus manchouricus, and the secondary hosts are the same mollusk and Boreoelona ussuriensis. Specimens of the new species are similar to A. amnicolae identified by Stunkard in 1959, but the mature worms have larger suckers and shorter ceca. The cercariae of these species are distinguished by body, suckers and pharynx size. These organs in A. perccotti sp. n. are more than one-third larger than what is observed in A. amnicolae. In addition, the new species lacks the capacity for progenesis. Finally, the new species is unusual in that it resides in the fish esophagus instead of the intestine, as is common for most Asymphylodora species. Partial ribosomal DNA sequences and phylogenetic reconstruction sequence data indicate that these worms represent a new digenean species.