[Specific features of the numbers and structure of the population of Proteocephalus longicollis (Zeder 1800) (Cestoda: Proteocephalidea)--a mass parasite of whitefish Coregonus lavaretus L. under conditions of technogenic pollution of the water body].

The numbers, age structure, and morphological variation of the cestode Proteocephalus longicollis from whitefish of a natural water body (Kamennoe Lake) and those of Kostomuksha Lake polluted with wastes of the mining industry (Northern Karelia) have been studied. In the polluted water body, a high infestation of whitefish and domination of larval stages in the structure of the parasite population have been established. It is shown that under conditions of pollution, only one of the variations ofscolex signs dominates in the structure of phenotypic diversity.

[Polymorphism and intraspecific variability in the cestode Proteocephalus tetrastomus (Rudolphi, 1810) (Cestoda: Proteocephalidae), a specific parasite of smelt (Osmeridae)].

Morphological variability in the cestode Proteocephalus tetrastomus parasitizing smelt in Lake Ladoga (Baltic Sea basin) and Lake Goluboye (Pechora River basin) was studied. Two forms of P. tetrastomus differing in the proglottid structure, and two variations of the ovary were discriminated.

[Populational variability of Proteocephalus longicollis (Cestoda: Proteocephalidae) in the vendace Coregonus albula from lakes of Karelia].

Populational variability of Proteocephalus longicollis from the vendace inhabiting various types of Karelian water bodies was studied. High phenotypic diversity of the helminth and polymorphism in the cestode's major functional complexes - attachment, trophic and reproduction - are established. High degree of phenotype pool realization was determined for various P.

[Successional features of the dynamics of abundance and population structure of the cestode Proteocephalus longicollis (Zeder, 1800) (Cestoda: Proteocephalidae)].

Dynamics of abundance and changes of populations structure were investigated in a host-specific parasite of salmonids, cestode Proteocephalus longicollis from the vendace Coregonus albula L. of the Syamozero Lake during the period of more than forty years. A relative stability of the values of infestation indices independently of significant changes in the abundance and population structure of the vendace is established.