Features of parositofauna Esox lucius (Linnaeus, 1758) of the Tabol river in the winter period of the life cycle

The article presents the results of a complete parasitological study of Esox lucius, which inhabits the Tobol River, in the winter period of the life cycle. Infection with 10 species of parasitic organisms belonging to six systematic groups was established: Ciliata-2, Sporozoa-1, Myxosporidia-3, Monogenea-2, Cestoda-1, Trematoda-1. Parasitizing Apiosoma sp. and T. esocis is recorded on the fins, body surfaces and gills, the intensity of invasion is not significant, the extent of infestation (EI) is 37.5% and 31.2%, respectively. Invasion of H. lobosa and H. psorospermica was established on the surface of the gills, EI was 31.2% and 37.5%, respectively. In 25% of the pike, a study of the kidneys revealed a lesion of their tissue Mixosoma sp., AI from 3-8 spores. As a result of microscopy of blood smears, infection of fish with intra-erythrocytic parasites - H. esoci, EI - 18.7%, the percentage of infected red blood cells averaged 0.1 ± 0.03%. On the fins of fish, G. lucii with an EI of 25% was found, the abundance index (AI) was 1.7 copies per fish of the whole sample. A 100% infection of the gills of T. monenteron was established, the AI constituted 175.9 specimens. Only A. lucii trematode was parasitized in the stomach, the EI was 100% and the IO was 43 copies per each individual examined. All individuals of A. lucii were sexually mature, which indicates the infection of fish in the spring-summer period during active feeding. Cestoda T. nodulosus is found in the intestine of the pike in sexually mature form with EI - 100% and IO - 53.9 specimens. In the Tobol river, T. monenteron - D = 64.1% is dominant in this pike, subdomination was noted in T. nodulosus (D = 19.6%) and A. lucii (D = 15.7%), low level of dominance in G. lucii - D = 0,6%. At the age of 2+ to 6+ pike invaded by T. monenteron, T. nodulosus and A. lucii in 100% of cases. Parasitization of G. lucii was observed in fish from the age of 4+ with a gradual increase in AI by the age of 6+. Mixosoma sp. and T. esocis are noted only in the age groups 2+, 3+ and 4+. H. lobosa was recorded on the gills of fish from the age of 4+ to 6+, H. psorospermica occurred in groups of 3+ - 5+, Apiosoma sp. parasitized the pike from 2+ to 5+ years. The intra-erythrocyte H. esoci parasite was noted in only three pike specimens at the age of 4+ (1) and 5+ (2). Biological diversity in the parasitic community of E. lucius of this ecological system during the winter period of the life cycle is rather poor and is represented mainly by the simplest and narrowly specific parasites.