Parasitic <i>Cyathocephalus Truncatus</i> cestodes as an indicator of localization of self-naturalized populations of American char (<i>Salvelinus Fontinalis</i>) in the Strelka River basin

Abstract

The Northwestern Federal District holds a leading position in the commercial fish farming of the country. In particular, the Leningrad Region occupies the second place among producers of commercial fish in the region, the fisheries complex of which includes 200 enterprises. The main object of aquaculture is rainbow trout (97.1%). Parasitic diseases often occur in fish farms. To make a diagnosis, a comprehensive examination is carried out, including the collection of epizootological data, a clinical examination, a diagnostic autopsy and laboratory tests. This article describes a case of cyatocephalosis epizootics in an operating fish farming. The causative agent of the disease is Cyathocephalus truncatus cestode, belonging to the order Pseudophyllidea, family. Cyathocephalidae. It parasitizes the pyloric appendages of mainly salmonid fish. The development of C. truncatus occurs with the participation of one intermediate host, which are crustaceans: Rivulogammarus pulex, R. spinicaudatum, Pontogammarus bosniacus, Pontopereia hoi, Pallasea quadrispinosa. To determine the causes of infection of rainbow trout juveniles, an assessment of the infestation of final and intermediate hosts, the seasonality of invasion in 2021-2022, as well as control catches of the head pond and Mill Creek belonging to the Strelka River basin was performed. During the study, 16 individuals of different ages of American char were caught, 6 of them were subjected to a partial parasitological autopsy for infection with cyatocephalosis. As a result of the study, C. truncatus cestodes were exposed in all individuals in an amount from 2 to 5. Consequently, the absence of cases of progenesis in procercoids of intermediate hosts of gammarid crustaceans, infection with parasitic cestode of both final and intermediate hosts allowed us to conclude that the final hosts of the parasite, salmon-like fish species, are present in the enterprise's water supply system. Thus, the parasitic cestode contributed to the self-naturalization of the American char population, the reproduction and cultivation of which in this water source ended in the 1970s, and has been considered lost until now.