First record of metacercariae trematodes Opisthioglyphe ranae (Digenea: Telorchiidae) and Echinostoma bolschewense (Digenea: Echinostomatidae) in Dreissena polymorpha (Bivalvia: Dreissenidae) from the Don and Volga river basins, Russia

It is well known that an invasive bivalve mollusk species Dreissena polymorpha plays a significant role as a host to parasites. Currently, the interaction between digenean trematodes and their bivalve hosts remains relatively poorly understood. In this study we investigate infection of D. polymorpha by trematodes using molecular genetics, histological, and light microscopy methods. We obtained sequences of one mitochondrial (molecular cytochrome c oxidase subunit 1 (COI)) and two nuclear (ITS2, rDNA 28S) gene markers. To the best of our knowledge, this is the first time that infection of metacercariae of Opisthioglyphe ranae and Echinostoma bolschewense in D. polymorpha has been detected. Our sequence was 100% identical to the 28S rDNA of the species O. ranae recorded in Penza Oblast (Russia) in pond frog. At the same time, some sequences of the 28S rDNA of O. ranae detected in Penza Oblast (Russia) and Ivano-Frankovsk Region (Ukraine) were different from our sequence by 0.2%. Our sequence was 100% identical to the 28S rDNA of the species E. bolschewense sequenced in Slovakia. In addition, we received sequences of COI for both trematode species and ITS2 of E. bolschewense for the first time.

Molecular data on Phyllodistomum macrocotyle (Digenea: Gorgoderidae) from an intermediate host Dreissena polymorpha (Bivalvia: Dreissenidae) in the Northern Dvina River Basin, Northwest Russia

We report the first molecular identification of Phyllodistomum macrocotyle (Digenea: Gorgoderidae) from the Northern Dvina River Basin, Northwest Russia. Comparative analysis of our sequence was 100% identical to the 28S and ITS2 rDNA sequences of the species P. macrocotyle in zebra mussels discovered in Poland (Wigry Lake), Lithuania (Elektrenai Reservoir and Sirvinta River), Russia, Belarus (Lepelskoe Lake and Lukomskoe Lake), and in fish Leuciscus idus, Scardinius erythrophthalmus in Russia (Rybinsk Reservoir on the Volga River). At the same time, some sequences of the 28S rDNA of P. macrocotyle in zebra mussel detected in Lithuania, and Belarus were different from our sequence on 0.2-0.6%. The ITS2 sequences which have 100% similarity with our specimens of P. macrocotyle were discovered in sporocyst of phyllodistomes from its intermediate host D. polymorpha in Poland, Lithuania, Russia, and Belarus. Our observation in the Yuras and Isakogorka rivers represents the northernmost record of this host-specific parasite, to the best of our knowledge.