Diversity and Distribution of Opisthorchid Metacercarias in Fish in Water Bodies of Urbanized Territories

The characteristics of the biodiversity of opisthorchids and the infestation of additional hosts in various aquatic ecosystems in a metropolitan area (Novosibirsk city) are presented. The objectives of this study included determining the species composition of opisthorchids metacercariae, analyzing their occurrence and abundance in fish in each of the three groups water bodies, namely: the Ob River, its tributaries, and Berdsk Bay, located within the boundaries of Novosibirsk city and differing in the set of abiotic and biotic characteristics. The composition of the metacercariae hemipopulation in the surveyed water bodies was identical, being represented by three species, namely, Opisthorchis felineus (Rivolta, 1884), Metorchis bilis (Braun, 1890), and Metorchis xanthosomus (Creplin, 1846). However, the infestation of an additional host by opisthorchid larvae of individual species in different water localities was variable and was determined by local environmental features. The most common opisthorchid species in fish caught in the Ob River and Berdsk Bay is O. felineus, the subdominant ones are M. bilis and M. xanthosomus, respectively. In Berdsk Bay small local fish were most frequently and intensively infected with O. felineus (ide, gudgeon, and dace) and M. bilis (ide, gudgeon), while in the Ob River, O. felineus and M. xanthosomus metacercariae were more often recorded in commercial ide. In the additional host inhabiting the Ob tributaries, unlike other water bodies, M. bilis and O. felineus were dominant, with M. bilis metacercariae more often detected in small local fish, gudgeon and ide, and O. felineus, in small-sized roach. Our analysis of the diversity of opisthorchid metacercariae representatives using biological indices indicates a simplified structure of opisthorchid communities in each water body. The most complex structure of the opisthorchid hemipopulation was found in the Ob tributaries (H = 1.01), then in Berdsk Bay (H = 0.51) and in the Ob River (H = 0.32). The highest values of dominance indices (D) are characteristic of the main channel of the Ob and Berdsk Bay, which indicates the abundance of one species of opisthorchid, namely, O. felineus. Low values of the Simpson index in the Ob tributaries indicate the uniformity of the abundance of metacercariae and the absence of obvious dominance of any species.