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157 specimens of Salmo salar L. belonging to different age groups were examined in the region of the Lower-Tuloma hydropower-station. 13 species of parasites (of them 5 are freshwater) were found in anadromous migrants. The character of the parasite fauna and the structure of fishes' scale have shown that some salmons cannot get the fishrunning over and stay in summer months under the damb where become infected with freshwater parasites. 19 species of parasites (of them 14 are freshwater) were found in catadromous migrants. These fishes cannot penetrate through the damb of hydroconstruction beyond the limits of the reservoir and pass here to an active feeding that is indicated by a rich composition of freshwater parasite fauna. The infection of adult salmons with plerocercoids of Triaenophorus crassus during the spawning migration points to the presence of trienophorosis nidus in this water reservoir. Parasite fauna of salmon smolt, represented by 7 species, is not affected by the water reservoir and hydroconstruction. The smolt does not stay too long in the reservoir and early stages of its seaward migration do not coincide with the termination of the developmant of the invasional stages of procercoids of Pseudophylidea.

Migratory abilities of Bithynia inflata have been studied. The investigations have been carried out in the West-Siberian nidus of opisthorchiasis during four summer seasons since 1975. Mollusks were marked with isotopes ⁶⁰Co and ^110mAg. It has been established that the mollusks do not migrate for long distances, prefer to lead a settled life and do not leave their constant biotopes even during spring floods. Migrations of mollusks within their biotopes take place, in general, along the shore line. After drying of water mollusks spend this unfavourable period in surface layers of the bottom mud or under the layer of vegetation litter-fall.

The daughter sporocystes of Microphallus pygmaeus from the snails of Littorina saxatilis and L. obtusata were investigated. The average quantity of metacercariae in sporocysts is influenced by host species, its syze and by the season. There are differences in the average number of larvae from parthenites of L. saxatilis, collected in the Barents and White seas.

The occurrence of the species has been analysed on the basis of the authors' own data, collection material of some parasitological laboratories and literary sources. It has been established that Azygia mirabilis is a rare species with a low number of populations. Only in Lakes Kujto (northern Karelia) and Pechozero (the Kola peninsular) the species is abundant.

Certain peculiarities of the senescence of Ixodes persulcatus population were established according to the changes in the age composition of hungry adult ticks belonging to different groups. It was found that the expenditure of reserve nutrients is irregular, this irregularity being greater in males than in females. Early in season younger ticks become active while in the second half of the season — older ones. Maximum life span of females in fir forests of western Sajans is 70 to 80 days, that of males — 65 to 70 days. The average life span of females is greater than that of males. The conclusions are not precise enough that is mainly due to irregular character of senescence of ticks, to errors in representativeness, and subjectivism of the age evaluation in using qualitative criteria.

Under experimental conditions individuals of С. (Medioctenophthalmus) golovi golovi Ioff et Tiflov, 1930 complete their metamorphosis within a wide range of temperatures (from 28—30° to 2—6°) and at high humidity of 90 to 100%. The highest survival of larvae and cocoon stages was observed at 23—25° to 9—11°. The development from egg to imago lasts 28 to 557 days depending on the temperature and great extent of hatching under all conditions. Embryogenesis carries out 4—97 days. The ability of C. golovi to complete metamorphosis at 2—6° and to exist for a long time at the larval stage (up to 516 days) differs it from other souslik fleas and other species of Ctenophthalmus studied at the preimaginal stages.

Interspecies epizootic parasitic contacts between rodents, bearers of plague in Mujunkums, have been studied. Rhombomys opimus, Meriones meridianus and M. libicus were marked with different radioactive isotopes. A bilataral exchange with fleas between great gerbils and rodents of the genus Meriones has been established. The exchange proceeded in the direction from rodents of the genus Meriones to great gerbils. Theoretically each rodent of Meriones meridianus and M. libicus fallen ill with plague can transmit within 24 hours one "blocked" flea to a great gerbil. In autumn three of ten animals take part in such transmission.

Data are given on the fleas of Citellus musicus from Central Caucasus. Ecological peculiarities of fleas from the above region were compared with data known for fleas from plain Precaucasus. Differences between annual cycles of fleas of the same species from two altitude belts of the Baksan valley are considered. Epizootological significance of ecological peculiarities of fleas in the Baksan plague nidus is discussed.

The paper deals with the dynamics of age composition of M. richiardii females caught in their day shelters, near their biotopes during attacking and in the town park. The maximum number of gonotrophic cycles of this population and the ability for autogenic development of follicles in some females of the 1st generation were determined. The laboratory females were observed to differ in a higher degree of autogeny. The clutches of non-fertilized eggs were recorded.

Changes in proteins and immunobiological properties of cerebrospinal fluid and serum of blood during trypanosomosis of rabbits infected with T. ninaekohljakimovae are described. Changes of the protein composition and immunobiological properties in cerebrospinal fluid and serum have been shown to differ in the degree, character and time of their display. The dependence of changes in the concentration of immunoglobulins IgM, IgG, IgA (according to the data of immunoelectrophoresis) of blood serum on its protective properties was investigated. The role of cerebral barrier mechanisms in the formation of immunity in the central nervous system is shown.

The microsporidian Pleistophora carpocapsae does not influence the growth, development and mortality of its host — the caterpiller Malacosoma neustria L. On the other hand P. schubergi causes sireous desturbances of the insects functions: stimulation of growth just after the infection, its opression and retardation of development during the next stage of the disease. All this results in the fatal end.

Biological interrelations between the agent of microsporidiosis of the silkworm and local species of insects were studied. 7 species of Lepidoptera (Agrotis segetum, Chloridea obsoleta, Laphygma exigua, Plusia gamma, Pieris brassicae, P. rapae, Lymantria dispar) were infected with the suspension of Nosema bombycis spores. Results have shown that 6 species of insects are susceptible to Nosema bombycis excluding only the gipsy moth. So, N. bombycis can be considered to be a parasite with a wide range of hosts.

In contrast to macrurids from the Pacific, for which 5 species of myxosporidia of the genus Myxidium are known, only one species, M. coryphaenoidium, is recorded for this group of fishes from northern Atlantic. In 9 of 13 species of macrurids there were found M. melanostigmum, M. melanocetum, M. noblei sp. n., Myxidium sp. M. coryphaenoidium, the diagnosis of which is rather wider and includes the parameters of other species, was not found. The spores found have a large size, rough polar filament, flattened ends of spores and unequal polar capsules. This favours apparently the sinking of spores to a considerable depth and so is an adaptation for parasitism in deepwater fishes.

A new genus and species of the marine parasitic nematode Abos bathycola gen. et sp. n. are described. The diagnosis of the new order Marimermithida with one family Marimermithidae Rubtzov et Platonova including 6 genera of marine parasitic nematodes is given. The new order resembles the order Mermithida in its extraintestinal feeding but differs from it in the following characters. The mouth, oesophagus, rectum and anus are reduced or absent. The mid-gut is transformed into trophosome, without lumen as a rule. If the lumen is present, no food is traced in the trophosome. The location of rudiments of oesophagus, chords, undeveloped trophosome, rudiments of rectum, if present, is consecutive. Stichosome is absent in contrast to the order Mermithida, in which it is well developed and is located in parallel with trophosome. Nematodes of the new genus are parasites of marine invertebrates unlike mermithids which are parasitic in land and freshwater arthropods and sometimes in mollusks.

A new species of ciliates of the genus Apiosoma is described. The species was found on the skin and gills of Leuciscus cephalus from the Kura river. Differential diagnosis of the species is given.

The entomopathogenic fungus Coelomycidium simulii Deb was found in pupae and imago of black flies of the genus Friesia from the mountains of Zailijsky Alatau (the Kazachka river). Pupae and imago were 6 and 4% infected with this agent respectively.

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Summary is absent.

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Summary is absent.