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Advances in sarcosporidian research within the latest decade are critically reviewed and analysed in respect to some recent cytological findings of the author and her colleagues on the subject. Three rather than two morpho-functional cell types (metrocytes and merozoites) are distinguished within the sarcocyst, the third one being the intermediate cell. Division by endodyogeny in the cyst of Sarcocystis is very likely confined to the latter cell type. The pattern of nuclear chromatin and the constancy in DNA value per nucleus in the cystic merozoites, revealed by flow cytometry, is rather indicative of their incapability of dividing within the cyst, i. e. in the intermediate host. This enabled us to consider these merozoites as homologs of coccidian gamonts. The obvious differences between cysts and cystic stages in Sarcocystis and Toxoplasma may account in part for the rare, if any, reported cases of congenital sarcocystosis in the intermediate host.

Fine morphology of the glandular system of young and mature cestodes of Dilepis undula is described. Glandular syncytium formed by modified cytons of tegument is located in the proboscis and proboscis-sheath. Three types of secretion, cords of the material of moderate density, rod-shaped bodies and vacuoles with dense material, are found in perikaryons, processes of glands and surface syncytium of the proboscis tegument of young cestodes. A new type of secretion, ovoid bodies, appears in mature cestodes. The apical part of the proboscis tegument is a zone of formation and secretion of vacuoles with light granular content. Functional activity of the granular system increases in mature cestodes. A possible functional role of scolex glands in cestodes is discussed.

The comparative analysis of karyotype of Notocotylus ephemera, N. attenuatus and N. imbricatus was carried out. The karyotypes of the embryonic cells of the above species consist of 20 chromosomes: most of them are biarmed. Studied species exibit distinct differences in chromosome morphology. The greatest karyological distance between N. imbricatus and two other species was revealed. During the processes of speciation and evolution of Notocotylus species the reorganisation of the chromosomal material was going on, in general, by means of pericentric inversions duplications and deletions. Two karyotypical morphs of N. ephemera (2n=20 and 2n=21) were detected.

After-effects of hybridization of S. mansoni strains, having Biomphalaria pfeifferi as an intermediate host, have been revealed for the first time. The crossing of two african strains (malarial-M and guinea-G), which have different compatibility rates with their specific intermediate hosts, has shown that hybrids display a higher virulence in respect to molluscs-hosts than maternal strains. The compatibility rate of the first generation hybrids with B. pfeifferi decreased, the breachs in the compatibility being the more significant the higher the degree of adaptation between the maternal strain and specific intermediate host. The infectiveness of the second generation hybrids in respect to molluscs of two populations of B. pfeifferi (M and G) virtually did not differ and varied in the ranges of mean values between the initial infectiveness of two maternal strains.

A description is given of a new nematode species, Cystidicoloides uniseriata sp. n., from the White Sea cod Gadus morrhua maris-albi. The species is determined on the basis of the following morphological characteristics: reproductive system peculiarity, eggs and tail form in females, form of spicules and correlation of their sizes in males, correlation of the oesophagus parts. An analysis of variability of morphometric characteristics of males and females reveals that the most constant features are: the length of pharynx, a distance from the nerve ring to the anterior end of the body, sizes of eggs and spicules. A description of the fourth stage larvae is given.

Experiments on laboratory cultures of Hyalomma asiaticum and H. anatolicumi have shown that at the nymphal phase sexual dimorphism manifests itself in statistically reliable differences between general sizes and mass of the body of male and female individuals. Larger nymphs moult mostly into females, small ones mostly into males. Reliable differences have, been noted in the sizes of scutum, gnathosoma and its appendages in male and female nymphs of both species. At the larval phase sexual dimorphism does not manifest itself in the sizes of individuals.

The paper concerns the age structure of the nymphal portion of settlement populations of Ornithodoros papillipes. The dependence of the age composition of intrapopulational groupings of ticks on the abundance level was established. Self-regulation of the number of ticks depending on the density of their groupings is suggested. Optimal for reproduction are groupings of 30 to 100 ticks; with further increase in density the rise in the number slows down.

A new genus, Montivagum gen. n., with the type species Leptotrombidium latum Schluger, Kudryashova, 1969 was isolated from the collective genus Leptotrombidium. Characteristic of the genus, key to species, description of two new species and redescription of five species are given. Two new synonyms are established.

The paper concerns the possibility of decreasing the number of tabanid flies on pastures by means of ball- and funnel-shaped traps (of the Manitoba type) with insecticides and expediency of using the above method for the cattle protection that prevents the milk productivity loss by 6.7 to 8.3%. In addition to the traps, a regular cattle dip with insecticides, which are most attracting for the whole complex of bloodsucking Diptera and zoophilous flies, offers promise in the control of tabanids.

Data are given on the distribution of the cysts of Myxobolus bramae, Dactylogyrus difformis, Diplozoon scardinii on the gills of rudd and on the dynamics pf the infection of fishes with these parasites in spring and summer. Dactylogyrids have two types of distribution (early summer and August) on the gills of their hosts. Dactylogyrids and diporps are suggested to have a tendency for distribution in least washed parts of the gills though they are distributed abundantly enough in other parts of the gills. The distribution of Myxobolus bramae cysts, apparently, does not depend on water currents passing through the gills that can be explained by their penetration into the gills along the blood vessels.

Bothitrema cotti sp. n. from Cottus poecilopus from the northern part of the Primorje Territory is described. It differs from two other species of the genus in morphology, sizes of anchors and marginal hooks, bars and supporting plates. The species is parasitic on the fish of another order in a different region of the world and in fresh rather than in sea waters.

Description and a differential diagnosis of a new species of cestodes, Aploparaksis belopolskajae sp. n., parasitic in Gallinago gallinago L. and G. media L. in the north of Siberia are given.

A new species of cestodes, Microsomacanthus mica sp. n., found in the blind gut of Melanitta deglandi (Bp.) from the Chaun lowland (north-western Chukotka) is described. M. mica sp. n. differs from close species (M. formosoides, M. hystrix, M. strictophallus) in a shorter blade of proboscis hooks (4 µ), the absence of armament on the cirrus and size of the latter (in M. mica the evaginated cirrus length does not exceed 10 µ). Data are given on the life cycle of the new species: larva from spontaneously infected Gammarus lacustris is described; mature individuals of M. mica sp. n. are obtained by means of experimental infection of nestlings of Clangula hyemalis (L.) with larvae from spontaneously infected G. lacustris.

Data on the distribution of ATP-activity (A) along the longitudinal axis of the body of Bothriocephalus scorpii are given. A has been shown to decrease from the head to the posterior parts of the body. However, A has been noted to increase a little on the part of the body where mature eggs are thrown out.

The effect of different concentrations of copper sulphate on the content level of carotinoid pigments in the haemolymph of Lymnaea stagnalis infected with parthenits of trematodes was studied. The content level of carotinoid pigments in haemolymph of molluscs steadily decreases with an increasing concentration of the toxicant. The mortality of experimental animals under such conditions rises considerably, the mortality of infected animals being much higher than that of non-infected ones.

Acanthors of Polymorphus magnus are surrounded with 4 embryonal membranes resembling in their ultrastructure these of P. minutus. The both species differ from the other species in a peculiar structure of the second embryonal membrane; other differences are negligible. Electron microscopic description of three varieties of inclusions situated in the spaces between the third and forth embryonal membranes and between the latter and the acanthor's surface is first given.

A description of a new parasitic isopode, Glossobius parexocoetii sp. n. (Isopoda, Cymoi Mae), from the Atlantic is given.

Summary is absent.

Summary is absent.