Abstract
It is well known that class Trematoda includes solely parasitic forms of flatworms. Therefore, they have developed diverse morphological and functional adaptations to the parasitic way of life. One of them is enormous fecundity, which allows quick and widespread settlement and finding hosts. Therefore, studying the reproduction apparatus of helminthes is the central problem of Parasitology. Studying functional morphology of the reproductive system of trematodes in general and its separate parts is of particular interest in addressing such a theoretically and practically important problem as direct regulation of endoparasites' fertility. This article presents thoruoug information about functional morphology of male reproduction apparatus in the Parastrigea robusta trematode, which is a parasite in the digestive system of common pochard (Nyroca ferina), which has not previously been studied and described in detail. As a result, the obtained knowledge about peculiarities of the structure of male reproductive system in trematode Parastrigea robusta will add substantially to the knowledge about particularities of the structure of male reproductive system of trematodes of Strigeidae family and endoparasites' fecundity in general.