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Ultrastructural investigation and functional and comparative anatomical analysis of tubular glands in Trombiculid mited Hirsutiella zachvatkini, Leptotrombidium orientale and Euschoengastia rotundata on different stages of their individual development are thoroughly conducted. Organization of glands does not undergo any changes (transformation or regression) in the course of ontogenesis of mites with quiescent stages. In the moulting processes only ectodermal excretory ducts of tubular glands, which accept the ducts of alveolar salivary glands, are replaced. The long paired tubular glands are contiguous by their passage to all main organs of mites (alveolar glands, brain, midgut, gonads) and terminate blindly at the level of excretory pore. Each of the tubular glands may be divided into two parts - proximal (or caudal) and distal (or frontal). The expanded proximal part has large intracellular cavities with long tight micro-villy and moderate basal plasma membrane enfoldings. Central lumen is usually narrowed with sparse short microvilly of apical plasma membrane of epithelial cells. This part of gland is obviously the homologue of sacculus of coxal glands of other Arachnida. The properly tubular distal part of gland is built up of prismatic epithelial cells with intensively developed basal labyrinth and irregular short microvilly on apical surface, and is the homologue of labyrinth of coxal glands of Oribatida. Excrete materials are not formed in cells or lumen of tubular glands. Tubular gland structure therefore corresponds to organization of transporting epithelia, so the tubular glands perform the function of aquatic-saline metabolism in mites, in particular, excrete redundant body fluid consumed during the feeding. Originally tubular glands are the excretory coelomoductes, which gradually lost their natural functions and joined with alveolar salivary glands in the highest trombidiform mites.

Gonotrophic relations, functional and age changes of ovaries examined in the fly Stomoxys calcitrans. Folliculs maturing, yellow bodies formation and removing, traheols stretching on ovariols surface reflect the function cycles of female sex system. Age changes manifest by accumulation of aging indications of organism, oxidations products, small granuls of lypophuscine in pedicel and lateral oviduct cells. Intensity of life-time colouring this parts increases from pale-lemon to yellow and brown by insects aging.

Eleven morphometric and four qualitative features of larvae, as well as 6 morphometric parameters of pupae of Odagmia caucasica, which had been collected in 5 geographically remote regions of Armenia, have been studied. In this work besides absolute values of features we have used their ratios (indices) that shows forms and propotions of different organs. It was found, that larvae taken from Bzhni and Getashen had asymmetry of bilateral characteristics and that there were differences in the level of morphometric features variability; the latter fact is connected with sex and phase of the insect. Study of chronological variability of populations from Bzhni, Getashen and Martuni has revealed differences in the nature of distribution of features. It was shown that the rate of differentiation between geographically isolated populations fluctuated in the range from 20 (Getashen) to 33% (Amassiya). Differences in the qualitative alternative features and in the rate of microsporidium infection distinguish the differentiation of populations from Bzhni and Amassiya, which is caused by anthropogenic factor in Bzhni and by isolating landscape barrier in Amassiya. Species-specific morphometric features were discovered; these were the indices of propotions of larva ventral sclerite and of pupa respiratory filaments.

In the territory of the former USSR 9 species of myobiid mites of the subgenus Microtimyobia (Myobiidae, Radfordia) have been recorded. Two new species are described: Radfordia alticolae sp. n. from Alticola argentatus (Severtzov) found in Kyrghizia and R. rufocani sp. n. from Clethrionomys rufocanus (Sundevall) found in Bashkhiria (Russia). Radfordia clethrionomys Fain et Lukoschus, 1977 stat. n. and Radfordia lemmus Fain et Lukoschus, 1977 stat. n. formerly considered as subspecies have been risen up to the species rank. A new diagnosis of the subgenus Microtimyobia, descriptions of new species, the list of species recently recorded, and the key to all species of the subgenus are given.

During 11 years (since 1983) populational and parasitological surveys of coexisting populations of Littorina saxatilis and L. obtusata were carried out at the west spit of the South Inlet of the Ryazhkov Island (Kandalaksha Bay of the White Sea). Ten species of trematodes were found. Species list of trematode parasites was identical for two host species, Microphallus piriformes was the commonest trematode species (infection prevalence by this parasite reached 51.5%). Levels of infection by any other species did not exceed several percent. It was shown that species composition of double infections was simply a reflection of the infection prevalence by the corresponding trematodes. So, the commonest species M. piriformes was found in double infections with all other trematodes. In most cases detailed analysis of coincidence of different trematodes in double infections has not revealed any deviation from the random pattern. The only exception to this were double infections by M. piriformes and M. pygmaeus, and by the pair of Himasthla sp. and immature sporocysts of microphallids of the "pygmaeus" group, which were rarer than expected. Deviation from the random pattern (tested by Chi-square statistics) was significant in 1983 and 1984 (for M. piriformes-M. pygmaeus combination) and in 1994 (for the second pair of parasites). Double infections by Himasthla sp. with mature microphallids of the "pygmaeus" group did not differ in frequency from the expected values. Triple infection were very rare. However, the observed frequencies of triple infections exceeded the expected values by 1-2 orders of magnitude. Above described peculiarities of trematode distribution were typical for populations of both snail hosts. In general, results of our study suggest weak (if any) interference between populations of different trematodes in the community. This is probably due to the species composition of parasites and the ratio of infection prevalence by different trematodes.

Morphological parameters of the cestodes vendace Coregonus albula - Proteocephalus exiguus and perch Perca fluviatilis - Proteocephalus percae were studied in facultative host - northern pike Esox lucius.

It was found out, that the cestode Microsomacanthus paraparvula Regel, 1994 being a common parasite of diving ducks in Chukotka uses a caddis fly Grensia praeteria (Trichoptera) as an intermedial host in its life cycle. Mature fragments of the cestode have been collected from droppings of the experimentally infected nestling of the kittiwake Rissa tridactyla (non-specific host) and used for the fine morphology study of embryonal shells and for an infection of intermedial hosts.

Crickets, being infected with two intracellular parasites Nosema grylli and Adelina sp., localised both in fat body cells, represent a good laboratory model for studying of host-parasite interactions. The deep physiological differences between two parasites allow to suppose the strike differences in their energetic and carbohydrate metabolism. The study of the activities of enzymes of energetic metabolism of the infected host cells contributes to understanding of the specific ways of influence of each parasite in the cell. Alterations of the lactate dehydrogenase (LDH) activities in fat body of crickets, infected with two intracellular parasites, have been studied using spectrophotometry. Infection with microsporidia caused 5-fold enhancement of LDH activity, infection with coccidia - 10-fold one. Polyacrilamid gel electrophoresis (PAGE) of supernatants from fatbody homogenates revealed three LDH isozyme patterns. After specific staining they form following bands: (1) a "slow" band; (2) a "fast" band; (3) a band with 5 distinct inner bands. These types of LDH isozyme patterns occur in studied males, females and larvae crickets, and thus the LDH variability seems not to be influenced by the sex and ontogenetic stage of hosts. Crickets, infected with microsporidia, also possess all LDH patterns, but we observed LDH isozyme pattern of type (2) neither in crickets infected with pure coccidia, nor while the mixed infection with both pathogens. The probes from infected crickets gave much more intensive stainig of isoforms. It is known that insect LDH is coded by one gene. Five bands observed may correspond to combinations of the products of different alleles of this gene inside the LDH molecule, that possesses a tetramerous structure. Our data may indicate to the existence of LDH polymorphism in cricket populations.

600 Golden Hamsters were divided into 3 groups: 1 - free from Opisthorchis invasion, 2 - once infected, 3 - repeatedly infected. Seasonal variability of liver, portal and mesetery lymph node and adrenal gland relative mass was infestigated in winter, spring and autumn. Diurnal stereotype variability of parenchymatous and lymphoid organ relative mass is associated with a season and invasion number, and in a considerable degree is reflected in the meaning of average diurnal index.

A description of the new species Phyllodistomum pungitii sp. n. (Trematoda: Gorgoderidae) from the kidney channel of Pungitius pungitius taken from a freshwater lake of north-western Chukotka is given. The difinition of this species is also confirmed by the karyological method of investigation.

Morphological analysis of representatives of polyphyletic genus Dactylogyrus of the world fauna revealed, that some monophyletic groups of these worms display independent changes in a hard structure of haptor, or in a structure of copulatory organ. For example, in case of a identical haptor structure in such groups as D. sphyrna (5 sp.), D. varicorhini (18 sp.) and D. pseudanchoratus (32 sp.) the morphology of copulatory organ varies from a straight tube (sometimes without accessory piece) to spiral-sphaped tube and complicated accessory piece. Contrary, D. bicornis (7 sp.), D. catlarius (10 sp.) and D. afrobarbae (29 sp.) being identical in copulatory organ morphology have a great variety in the hard parts of haptor up to loss of the anchors and bars. All these groups of species have a strict specificity for definite groups of fishes and show co-evolution of parasites and hosts and therefore the origin of species cannot be explained by a transmission worms to other fishes groups (host switching, colonization, etc.). More over, independent changes of these characters do not related with geographical variations. On my opinion, the only mechanism leading such origin of species is explained by the theory of r-K strategy of selection. An alternative realization of different poles of continuum of these strategies, probably, leads to morphological changes either copulatory organ (r), or haptor (K). Majority of others monophyletic groups of this genus, both hard parts of haptor and copulatory organ are changed simultaneously.

It is shown, that spores of the microsporidia Myxobolus pfefferi Thelohan, 1895 do not differ from the spores of M. muelleri Butschli, 1882. Spores of M. pfefferi display a great variety in the disposition of anterior ends of polar capsules, namely from adjacent to widely separated. A reaction of a host could not be used as a prove of a species validity. M. pfefferi is considered as the junior synonym of M. muelleri.

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