SOME FEATURES OF THE PARASITE FAUNA OF VENDACE <i>COREGONUS ALBULA</i> UNDER CONDITIONS OF LAKE PLESHCHEYEVO
This study investigates the parasite fauna of vendace Coregonus albula from Lake Pleshcheyevo. Significant disturbances of oxygen regime in the deep part of the lake at high water temperatures of the upper layers, which substantially reduces the comfort zone of the fish during its feeding period, is typical for this waterbody. A com- parative analysis of changes in the parasite fauna of Pereslavl vendace over a long-term period has been made. It has also been found that these changes occur in a reduction in species richness of parasites typical for the coregonid fish (Coregonidae). At present, vendace from Lake Pleshcheyevo can be considered as an example of an endemic population of the species Coregonus albula at the southern limit of its initial range. The absence of monogenea, Discocotyle sagittata (Leuckart, 1842) - a specific parasite typical for the salmonid and coregonid fish - can be considered as evidence of the population marginal status. During the feeding period vendace from Lake Pleshcheyevo can serve as an example of an obligatory pelagic planktophagous fish. In this case, frequent occurrence of a specific cestode, Proteocephalus longicollis , (up to 100%) indicates a high density of the population under relatively favorable ecological conditions. Most of the 11 parasite species typical for vendace from Lake Pleshcheyevo don't exhibit rigid specificity to the host: Dermocystidium percae Reichenbach-Klinke,1950; Proteocephalus longicollis (Zeder, 1800); Diplostomum spathaceum (Rudolphi, 1819); Tylodelphys clavata (Nordmann, 1832); Ichthyocotylurus variegatus (Creplin, 1825); Ichthyocotylurus erraticus (Rudolphi, 1809); Rhipidocotyle campanula (Dujardin, 1845); Camallanus lacustris (Zoega, 1776); Piscicola geometra (Linnaeus, 1761); Ergasilus sieboldi Nordmann, 1832; Argulus foliaceus (Linnaeus, 1758).