[NUMBER DISTRIBUTION AND POPULATION STRUCTURE OF PROTEOCEPHALUS LONGICOLLIS (ZEDER, 1800) (CESTODA: PROTEOCEPHALIDEA), A PARASITE OF SMELT AND COREGONIDS].

The spatial structure and seasonal aspects in the number distribution of the cestode Proteocephalus longicollis population, maintained by trophic connections of specialized plankton-feeders (the vendace Coregonus albula L. and the smelt Osmerus eperlanus L.) in the Lake Onego were studied. Differences in the distribution of number of cestode population in host population, size-age structure, and pre-reproductive/reproductive stages ratio of the studied parasites were revealed. It was demonstrated that the spatial structure of P. longicollis was shaped by the specific characteristics of vendace and smelt populations in the Lake Onego. These species possess partially overlapping ecological niches and differences in the use of food resources, significantly determining the infection dynamics of the examined fish species.

[MORPHOLOGICAL VARIABILITY OF PROTEOCEPHALUS PERCAE (MÜLLER 1780) PARASITIZING COREGONID FISHES].

Morphological variability of Proteocephalus percae from native host--perch Perca fluviatilis and two species of coregonids (whitefish Coregonus lavaretus and Arctic cisco C. autumnalis) from fish farms of Karelia were studied. Parasite groups from 3 host species differed by morphometric parameters. Morphological structure of P. percae from native host included three morphs, those numbers were almost equal. Parasite groups of whitefish and Arctic cisco differed from that of perch in morphological structure and dominance of different morphs. Changes of the P. percae morphological structure was related to differences in ecological niches of three hosts of parasite. This reflects the initial stages of microevolution. The results obtained allow us to estimate an adaptive response of parasitic worms to new host species settling to pond.

[Ecological and Biochemical Aspects of Parasite-Host Interactions in Transformed Aquatic Bodies: A Case Study of the Cestode Triaenophorus nodulosus and Its Host, the Northern Pike Esox lucius].

The lysosomal enzyme activities of the cestode Triaenophorus nodulosus and its host, the pike, in-aquatic bodies with different degrees of technogenic transformation (Northern Karelia, Russia) have been studied. As has been shown, iron-ore waste causes an increase in the acid phosphatase, nuclease, and beta-galactosidase activities of the host and a decrease in its beta-glucosidase and cathepsin D activities. As a rule, the changes in the same cestode enzyme activities are the opposite. With a decrease in the technogenic load, most of the studied characteristics display the trend of approaching the corresponding values observed in a clean lake. It is assumed that the host plays a leading role in the biochemical adaptation of the parasite and its host to mineral environmental pollution.

[PARASITES OF THE COMMON ROACH (RUTILUS RUTILUS L.) UNDER THE IMPACT OF INDUSTRIAL POLLUTION OF A LAKE].

The consequences of man-induced transformation of Lake Kostomukshskoe (tailings dump) related to increased mineralization and entry of highly dispersed dredge material not typical for northern lakes were studied using roach parasites as the example. It was found that the roach parasite fauna has been losing rare and scant parasite species of different taxonomic groups, mainly helminthes with an indirect life cycle. Common and dominant species of myxosporidians, monogeneans, trematodes of genera Diplostomum and Tylodelphys have been preserved. The chances of survival are higher for those parasites with direct life cycle. Also the parasite species whose larvae can actively penetrate the host have been survived. The species Ligula intestinalis, Philometra rishta, Pseudocapillaria tomentosa had reported very rare. Fish are infected with these parasites by feeding of Copepoda and oligochaetes.

[Morphological variability and the structure of pre-reproductive age group of the cestode Proteocephalus torulosus from Altai osman (Oreoleuciscus, Cyprinidae) in water bodies of Mongolia].

Morphological variability of immature Proteocephalus torulosus was studied for the first time. On the basis of scolex shape, three phenotypes were distinguished: clavate, rounded, and lanceolate. The clavate phenotype was found to be dominant, the rounded one is small in number, and the lanceolate one is rare. The wide ranges of morphometric variability were established. The clavate phenotype differs from the rounded one by its higher variability. The high morphologic variability of immature P. torulosus is comparable to that in adult mature parasites from Altai osman, the Central Asian endemic from the genus Oreoleuciscus. The conclusion is made on the influence of extremely changeable environmental condition in the region on the parasite and host adaptations during their co-evolution.

[Morphological variability and population structure of the cestode Proteocephalus longicollis (Zeder, 1800) in aquaculture].

Morphological variability of the cestode Proteocephalus longicollis (Zeder, 1800) from Coregonus peled (Gmelin, 1789) was studied in natural host population from the Pelyadka River and in aquaculture from the Kuchak Lake. Variability of morphometric characters of the parasite is recorded. Sample from the Kuchak Lake differs from the sample collected in the Pelyadka River by a greater number of testes, larger size of worms, smaller size of cirrus bursa and smaller ratio of the cirrus bursa length and the width of proglottid.

[Population biology of cestode genus Triaenophorus in natural and man-made water bodies].

A comparative study of the frequencies of occurrence and distribution of the abundances of pike parasites, tapeworms of the genus Triaenophorus, was carried out in natural lakes and water bodies contaminated by the Kostomuksha mining and concentration mill (Northern Karelia). We demonstrate that the wide presence of T. crassus and T. nodulosus in natural northern lakes is due to the diversity of aquatic organisms and the structure of trophic relations. The abundance of both species is modeled by the negative binomial distribution. Relations in the host-parasite system are stable. Estimates of the parameter k of the negative binomial distribution reflect the changes in the interactions in the host-parasite system. T. nodulosus has survived in the man-made water body storing the highly mineralized recirculated water from the mill. Disturbance-related distinctions were detected in the parameters of the T. nodulosus abundance distribution in the host population. In the Okunevoye Lake, where the water discharged from the tailings dump is more diluted, the infection rates in pike did not differ from those in undisturbed water bodies.

[Microevolutionary aspects of morphological variability and specificity of cestodes by the example of Proteocephalus longicollis (Zeder, 1800) (Proteocephalidae), a parasite of Coregonids].

Morphological variability of the cestode Proteocephalus longicollis from the smelt Osmerus eperlanus L., which was spontaneously introduced into the Syamozero Lake, has been studied. It was established that P. longicollis became an abundant element of the smelt parasite fauna during last 20 years, thereby showing the absence of host specificity. It was revealed that morphological polymorphism of P. longicollis from smelt combines features of ecological forms characteristic for aboriginal host species, namely whitefish Coregonus lavaretus L. and vendace Coregonus albula L. Cestodes from smelt are more similar to ecological forms from whitefish by the characteristics of variability. It is concluded that colonization of a host species, which is new for a given water body, is accompanied by the forming of a new group of host, which contributes to the maintenance of the parasite number and to its population stability under changing conditions of freshwater ecosystems.

[Morphological polymorphism of the cestode Proteocephalus longicollis Zeder, 1800 (Cestoda: Proteocephalidae) through the ontogeny].

The qualitative diversity of Proteocephalus longicollis through the ontogeny was studied: procercoids from copepods, immature and mature cestodes from the vendace Coregonus albula L. The structure of the P. longicollis population was found to be made up of the dominant phenotypes: by the scolex shape--Sc2, by the sucker arrangement type--SI, by the proglottid shape--P3, by the ovary lobe shape--01, by the testes arrangement type -T2. Some rare and scant phenotypes are also present. It is shown that the structure of the parasite phenotypes is relatively stable through the ontogeny. The assumption is made about the high survival rate of the S2 sucker phenotype.

[Phenotypic variability of a perch parasite-cestode proteocephalus percae (Müller, 1780) (Proteocephalidea) in different parts of the species range].

Discrete variability of four P. percae characters of the main cestode functional complexes was identified. Phenotypic diversity of P. percae from different parts of the distribution range was analysed. Research revealed low geographic variability and high stability of the dominant variations in combination with morphometric plasticity. The conclusion was made that the patterns of P. percae morphological variability were shaped by the common fate and long-standing co-evolutionary relations between the parasite and the host--the perch Perca fluviatilis.

[Polymorphism and structure of the population of Proteocephalus longicollis Zeder, 1800 (Cestoda: Proteocephalidae) in the vendace Coregonus albula L]. / Polimorfizm i struktura populiatsii Proteocephalus longicollis zeder, 1800 (Cestoda: Proteocephalidae) iz evropeiskoi riapushki Coregonus albula L.

Polymorphism and phenotypic diversity of a hostal ecoform of Proteocephalus longicollis from its typical host, the vendace, Coregonus albula L., were studied. A complex phenotypic structure of the parasite population and presence of morphologically different groupings were revealed. We distinguished four groupings based on the external characters and three groupings based on the feed and reproduction features; among latter groupings one has very specific variations of features. We conclude that P. longicollis has high intraspecific and intrapopulation heterogeneity, and the host plays a stabilising role in the parasite species formation.

[Variability and phenotypic structure of Proteocephalus torulosus (Cestoda: Proteocephalidea)--a parasite of cyprinid fishes]. / Izmenchivost' i fenotipicheskaia struktura Proteocephalus torulosus (Cestoda: Proteocephalidea)--parazita karpovykh ryb.

Variability of 5 qualitative features of Proteocephalus torulosus from 6 fish species belonging to 5 genera of the subfamily Leuciscinae was studied. Itraspecific diversity is represented by 3 scolex forms, 2 types of proglottid structure, 3 proglottid shapes, and 2 variations of the female reproductive system characteristics. The parasite living in different host species form separate ecological forms differing in the number of phenotypes and their ratio. However, the same scolex and strobila phenotypes dominate in the range of the parasite. Two P. torulosus groupings have been recognised the European and Asian ones, which differ in the representation of the proglottid structure types.

[Phenotype structure and its dynamics at different stages of the reproductive period of Proteocephalus osculatus (Cestoda: Proteocephalidae)--a parasite of catfish (Silurus glanis L.)]. / Fenotipicheskaia struktura i ee dinamika na raznykh étapakh reproduktivnogo perioda Proteocephalus osculatus (Cestoda: Proteocephalidae)--parazita soma Silurus glanis L.

Discrete variability of four P. osculatus characteristics descriptive of cestodes' major functional complexes: attachment and trophic-reproduction, was determined. Phenotypic diversity of P. osculatus from 2 samples collected at different stages of the population reproductive period was analysed. Unequal adaptation of phenotypes to the ambient conditions was hypothesised.

[The variability of the cestode perch parasite Proteocephalus percae in its host's geographic range]. / Izmenchivost' parazita okunia tsestody Proteocephalus percae v areale khoziaina.

Qualitative heterogeneity and its quantitative expression in geographically distant populations of Proteocephalus percae were studied. A wide spectrum of the possible values of the characters within which the expression of features is determined by environmental conditions, was detected.

[The morphological diversity of populations of Proteocephalus percae (Proteocephalidae) in the reservoirs of Karelia]. / Morfologicheskaia raznorodnost' populiatsii Proteocephalus percae (Proteocephalidae) v vodoemakh Karelii.

Morphological parameters of the cestode Proteocephalus percae which is common parasite of a perch were studied in four water bodies of Karelia. Significant morphological variability was observed within populations of the parasite. The phenotypic structure of certain populations of parasite is complicated and differs one population from another.

[The morphological variability of a population of Proteocephalus percae (Cestoda: Proteocephalidea) in Lake Rindozero]. / Morfologicheskaia izmenchivost' populiatsii Proteocephalus percae (Cestoda: Proteocephalidea) v ozere Rindozero.

The morphology of the cestode Proteocephalus percae, a typical parasite of Perca fluviatilis, from Lake Rindozero has been studied. The variability of 8 age groupings has been revealed and the connection of their morphological parameters with the specificity of host-parasite relationships at different developmental stages of the population has been shown.

[Parasite-host relations in toxascariasis in Arctic foxes]. / Parazito-khoziainnye otnosheniia pri toksaskaridoze pestsov.

The effect of host infection doze (10, 100, 1000 eggs) and developmental stages of helminths (larvae, adult nematodes) on the relationships in the system "Toxascaris leonina-Alopex lagopus" was studied experimentally. It has been established that 100 eggs are the threshold dose for helminths and 1000 eggs for the host. More distinct changes in the indices are characteristic of the parasite. Dynamics of host-parasite relationships in the development of the parasitic process correspond to helminth developmental stage. Larvae of T. leonina are most pathogenic for the host.