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The character of the distribution of the plerocercoid D. interrupta in the bream Abramis brama from the Kuibyshev water reservoir was studied. The spread of the parasites in A. brama population is of complex character and changes with the increase of fish body length. The factors affecting the maintenance and regulation of the relationships in the host — parasite system (size composition of fishes, peculiarities of the host's genotype, values of occurrence of different numbers of the parasites, variability of plerocercoids) are discussed.

The seasonal maturation of four species of helminiths, Acanthocephalus clavula, A. lucii, Camallanus lacustris and Bunodera luciopercae, from the perch Perca fluviatilis is briefly described. It is noted that A. clavula, A. lucii and C. lacustris are found as mature worms in the intestine of the fish host throughout the year, whereas in Bunodera luciopercae there is a limited season of maturation. As a result of experimental studies it is suggested that B. luciopercae uses host gonadotrophin to initiate and stimulate the early phase of gametogenesis. The gonadotrophin may also activate the parasites'own endocrine system, which then takes over control of subsequent spermatogenesis and oogenesis. This formation is used for a hypothesis for seasonal maturation of helminths in the fish definitive host. It also provides a potential explanation for seasonal maturation of helminths of fishes in polar and tropical zones of the world.

The paper presents data on the variability of attachment organs in the cestode Triaenophorus crassus, a parasite of freshwater fishes. The greatest range of variability of all the characters is typical of whitefish, a fish with a long life cycle, while the shortest one is characteristic of vendace and young of trout. It is suggested that the stay of the parasite in fishes, associated with host age, is accompanied by the increase in average sizes of hooks and variability range. Such an approach together with the analysis of hooks variability gives the possibility to estimate the participation of secondary intermediate hosts in the circulation of the parasite in the water body.

Parasitological analysis of sockey salmon fry from the lake Azabachje has shown reliable differences in the infection between aboriginal and migratory in the lake fry with the nematode Cystidicola farionis from the swim bladder, that is connected with differences in the nature of their feeding and ecology. It was found out that the infection of migratory fry occurs only in the lake during feeding and wintering periods, one-summer-old fry 35 to 57 mm in length being primarily infected. Quantitative criteria (the abundance of immature nematodes of C. farionis, the type of feeding) were ascertained, which in combination with scale characters differentiate 95.9 per cent of fry into aboriginal and migratory.

Three new species of the subgenus Rhinozachvatkinia subgen. n. (Avenzoariidae, Analgoidea) are described from three species of Procellariiformes belonging to different families: Zachvatkinia (Rhinozachvatkinia) graciosa sp. n. from Pachyptila desolata (Procellariidae), Z. (R.) pelecanoidi sp. n. from Pelecanoides georgicus (Pelecanoididae), Z. (R.) zygoloba sp. n. from Oceanodroma leucorrhoa (Hydrobatidae). The new subgenus differs from the subgenus Zachvatkinia (s. str.) by modified gnatosoma (apical parts of chelicera and subcapitulum elongated and narrowed). This modification has a more stronger expression in females than in males. That is unusual for feather mites. Members of the subgenus Rhinozachvatkinia are not so closely related species than those of the subgenus Zachvatkinia (s. str.) because each of them possesses features that are unique for the genus Zachvatkinia. The peculiarities of the distribution of the genus Zachvatkinia among the hosts of the order Procellariiformes are briefly discussed.

Tissues of white mice in the place of the attachment of H. asiaticum larvae were examined by means of electron microscopy 2, 4, 24 and 72 hours after the attachment to the host. Fine structure of the cement sheath, peculiarities of its connection with host's tissues, fine structure of derm at different feeding stages of the tick are studied.

By means of artificial shelters there were obtained nests of shrews with their young ones. It was established that in the nests reproduction of the flea Palaeopsylla soricis gromovi and hatching of young imago took place. New data explain extremely rare finds of reproducing females of the species on trapped animals, primarily vagrant shrews. A close connection of the reproduction of P. soricis (fleas of the genus of southern origin) with breeding nests of the hosts is to be associated mostly with vagrant way of life of shrews and poor protection of their temporary shelters.

The history of description and state of knowledge of 17 species and 4 not identified to species forms of Leishmania, described from reptiles of the world, are traced. It is suggested to retain 10 species and 3 forms of Leishmania in the list of the subgenus Sauroleishmania as follows: L. (S.) tarentolae, L. (S.) hemidactyli, L. (S.) ceramodactyli, L. (S.) nicollei, L. (S.) gymnodactyli, L. (S.) adleri, L. (S.) hoogstraali, L. (S.) senegalensis, L. (S.) gulikae, L. (S.) sp., L. (S.) sp. I, L. (S.) sp. II. 7 species and one form, L. (S.) henrici, L. (S.) davidi, L. (S.) zmeevi, L. (S.) sofieffi, L. (S.) chame-leonis, L. (S.) phrynocephali, L. (S.) helioscopi, L. (S.) sp. Markov e. a., 1964 must be excluded from the above subgenus since their description does not correspond to the development of the life cycle of Leishmania from reptiles. Flagellata Protozoa from the peripheral blood and intestine of reptiles, which were regarded by some authors as a "leptomonad stage of Leishmania", appear to belong to the genera Proteromonas, Monocercomonas and other Protozoa.

The reversible conformational changes in porphirine of hemoglobine of mouse blood during malaria and under laser and tocopherol effects were studied by means of Raman spectroscopy.

A new species of cestodes from the intestine of southern elephant seal (Mirounga leonina L., 1758) inhabiting the Antarctic waters is described. The name to the new genus is given on the basis of the coiled shape of bothria while the name of the species is based on the size of eggs which are smaller than those of other Antarctic members of the family Diphyllobothriidae Lühe, 1910.

Three types of larvae of cestodes of the collective genus "Scolex" are identified. Of them procercoids with trilocular bothridia without additional suckers are referred to the genus Spiniloculus, those with bilocular bothridia without additional suckers to Uncibilocularis and those with monolocular bothridia without additional suckers to Anophryocephalus, Pedibothrium and Prosobothrium.

Peculiarities of relationships in the "Fasciola hepatica — Lymnaea truncatula" system were studied by means of hystological and hystochemical methods. Trematodes cause deep hystopatho-logical and hystochemical changes of the injured organs of L. truncatula. They are determined by mechanical destruction of mollusc's tissues under the effect of parasites and by intoxication of animals with temabolites of parasites. Under the effect of parasites the content of glycogen and phospholipids in hosts' tissues decreases while the concentration of neutral fats increases. In most cases, however, the infected hosts remain viable that under normal ecological conditions results in the preservation of the "F. hepatica — L. truncatula" system.

Two new species of the genus Chordodes from praying mantids (ton identified to species), Ch. curvicillatus sp. n. from Sumatra and Ch. ferganensis sp. n. from Fergana Valley, are described by means of light and scanning microscopy. These close species differ from other species of the genus by a set of types of areolae, characteristic processes on the surface of the cuticle. The species differ between themselves in characteristic only of Ch. curvicillatus pairs of areolae with hairs on the apex, scattered in great number on the surface.

Biological interrelations between ectoparasites from the colonies of great gerbil were studied experimentally. Hungry fleas Coptopsylla lamellifer are able to feed on the ticks Ornithodoros tartakovskyi infected with plague and in so doing be infected with plague agent. Such feeding is identified as "heterovampirism".

The distribution areas of the main plague vectors of Xenopsylla fleas (X. skrjabini, X. gerbilli, X. nuttalli) on Ustjurt are given for the first time. They are found to be of great practical significance in the evaluation of the epizootic situation.

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