Report on two rare Myostenostomum species (Platyhelminthes: Catenulida) from the Volga River Basin
Two rare catenulid species, Myostenostomum vanderlandi Rogozin, 1992 and M. bulbocaudatum Luther, 1960, were found in reservoirs of the Volga-Kama Biosphere Reserve (Middle Volga Basin, Russia) during a survey of microturbellaria in 2013. Both the species were recorded for the first time in the fauna of the Volga Basin, while M. vanderlandi, previously known only from water bodies of South America, was first found in the Holarctic. The morphological characters and geographical distribution of the species are discussed.