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Summary is absent.

Strains resistant to 100 mkg/ml of cyclocheximide (Chx^R100) and to 2.5 mg/ml of chloramphenicol (Cap^R2,5) were used in studies for the presence of genetic interchange in C. oncopelti. Phenotypes of these strains were stable on the non-selective medium and specific. Strains Chx^R100 and Cap^R2.5 were mixed in equal proportions, cultivated during 7 days and tested. Under consecutive effect of inhibitors the culture of strains mixture and clones isolated from it exhibited bouble resistance. Phenotypes of recombinant clones were stable on the non-selective medium during, at the minimum, 70 to 90 cell generations. At the same conditions control cultures of parental strains and clones did not exhibit resistance that excludes the possibility of origin of cells resistant to both antibiotics from Crithidia of one of the parental strains as a result of secondary mutation. Thus, the results obtained show convincingly the presence of genetic interchange between Flagellata of Chx^R100 and Cap^R2,5 strains.

Three new species of Microsporidia from muscules of Orchestia bottae, Dikerogammarus villosus and Pontogammarus crassus of the Dnieper basin are described. Spores of Glugea orchestiae uninuclear, oval 4.35 (4.0—4.9) X 2.63 (2.3—3.0) mkm, in 4 spored sporophorous vesicles. Spores of Nosema dikerogammari binuclear, marrow-shaped 4.3 (3.7—4.8) X 1.9 (1.7—2.2) mkm. Polaroplast occupies 2/5 of the spore. Spores of N. pontogammari binuclear, oval 2.3 (2.1—2.8) X 1.5 (1.2—1.8) mkm. Polaroplast occupies 1/3 of the spore.

The effect of solutions of phenol (100, 250, 400 mg/l), copper sulfate, carbophose and bazudine (0.01, 0.1, 1.0 mg/l) on physical and chemical properties of haemolymph of Lymnaea stagnalis (L.) and Planorbarius corneus (L.) infected with parthenits of trematodes was studied. Haemolymph viscosity decreases and its active reaction shifts to weakly acid one. Haemolymph density decreases only in solutions of carbophose and bazudine. With heavy infection the concentration of haemoglobin in haemolymph of P. corneus does not change under the effect of phenol but the total volume of haemolymph reduces considerably.

Analysis of the age structure of parthenits of trematodes of sympatric populations of L. obtusata and L. saxatilis was conducted in 1983 for 6 localities in Kandalaksha Bay of the White Sea. 10 species of trematodes were found. The main populational differences in the level of infection are caused by Microphallus piriformes. Species with secondary dispersion in the life cycle are characterized by the increase in the infection extensity of populations with age. In Microphallidae species of "pygmaeus" group the age structure of infection depends on the overage infection of populations: the increase in the parasitic press leads to the maximum turning towards the young part of the snail's population. The establishment of the age structure of infection is considered to be one of the regulation mechanisms in parasite — host relations on the population level.

In southern Udmurtia, where occur both Dermacentor reticulatus and Ixodes persulcatus, in the years of high abundance of small mammals feeding periods of larvae and nymphs of these ticks coincide completely. The duration of simultaneous parasitism of preimago of the above ixodid species on animals is of epidemiological significance as far as within this period the infection of young stages of D. reticulatus with the virus of tick—borne encephalitis occurs. This is confirmed by the isolation of I strain of the virus from D. reticulatus collected at the state of engorged nymphs on hosts common with I. persulcatus and moulted in the laboratory.

Ear tags are a most effective method for protecting animals from ectoparasites for a long time with minimum expenditures and without polluting the environment. The method is based on a long evaporation of highly toxic insecticides, mainly pyretroids, homogeneously spread in the substance of the filler which by penetrating into the animal's hair provide its constant protection. Ear tags were successfully used for control of population of bloodsucking Diptera, mites and myiasis flies.

The data were obtained on the pathogenic effect of gregarinid Cephaloidophora pacifica Avdeev on crustecea Euphausia superba Dana. The high infection rate of the liver of E. superba with C. pacifica results in the tissue destruction and dark-brown colour of the organ.

The paper reports the finding of larvae of Scolex pleuronectis Müller, 1788 in the intestine of 42 northern fur seals on the Commander Islands. The description of the parasite is given.

A new species of cestodes, Microsomacanthus accuratus sp. n., from Clangula hyemalis L., a background species of Fuligulinae from the Chaun lowland (north-western Chukotka), is described. A brief characteristic of the new species is as follows: cestodes of medium size, length of immature specimens, terminating with hermaphrodite or young uterine proglottes 13 to 17 mm; length of hooks of proboscis 40 to 43 mkm, blade 10 to 11 mkm; bursa of the cirrus cigar-shaped, 201—259 x 40—46 mkm; cirrus with a wide armed basal part (14 to 19 mkm wide) and narrow (4 mkm) non-armed apical part, length of evaginated cirrus 35 to 37 mkm.

A figure and description of a new for Holarctic species of trematodes from Hydroprogne caspia Pallas, 1770 — Cardiocephalus musculosus (Johnston, 1904) Szidat, 1928 (Trematoda) are provided. The trematode is supposed to be brought from hibernation sites of C. musculosus.

A new trematode species of the genus Ciureana Skrjabin, 1923 from the intestine of the fur seal from the Commander Islands is described. The new species differs from other species of this genus in smaller size of the body, oral and genital suckers, testes, ovary and eggs, as well as in different host and place of finding.

A description and figure of the new species of trematodes of the family Didymozoidae, Didymonaja branchialis sp. n. found on gills of Thunnus alalunga from the north-western Pacific is given. The new genus Didymonaja gen. n. is erected for the new species.

Cheliceral sensillae of Hyalomma asiaticum were studied by means of scanning and transmission electron microscopy. In each chelicera there were found 30 sensory cells dendrites of which go into the cheliceral digits. 17 and 13 cells innervate sensillae of the mobile and immobile digits, respectively. The structure and location of cheliceral sensillae of H. asiaticum resemble much those of Boophilus microplus (Waladde, Rice, 1982) and Dermacentor variabilis (Sonenshine et al., 1984). Sensilla (LS) at the base of the mobile digit, which is innervated with one receptor cell and found only in H. asiaticum, is an exception.

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