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Morphological changes in organs and tissues of golden hamsters infected with different substrains of three species of Leishmania were studied by means of hystological, hystochemical and electron microscopy methods. Suspension of Leishmania promastigotes were administered intracutaneously to 495 animals. Detailed morphological analysis has shown that clinical differences in experimental leishmaniasis caused by three species of Leishmania are fully confirmed by morphological data. The studied species of Leishmania cause lesion of the skin specific for each species of the parasite. Thus, each of these parasites has its own characteristic type of relationships with a vertebrate host.

Results of the experimental study of the development of Markevitschia sagittata Kulakowskaja, Achmerov, 1965 in the external medium and intermediate host are given. Oncospheres begin to develop in eggs at a temperature of 18 to 26° С in 15—16 days. Their invasional properties manifest themselves in 32 to 35 days. In caudal segments of the worm oncospheres penetrate the body cavity through the intestine wall and then, depending on the maturation, migrate to the anterior end. In 58 to 60 days mature procercoids become localized in the anterior somites.

While studying the ultrastructure of the definitive part of cysticercoids of P. ciliata considerable differences in the tegument organization of proboscis, scolex and neck have been revealed. They manifest themselves in the thickness of the surface syncytium, the nature of inclusions, structure and density of microtrichia, nerve endings and in the distribution of glycocalyx. After excysting in 0.85% solution of sodium chloride at a temperature of 30°C intensive production by cytones of tegument and elimination of oval bodies into the surface syncytium begin. Functional role of local peculiarities of tegument of larval definitive parts is discussed.

The total content of free amino acids in the liver of fishes infected with plerocercoids of D. vogeli and D. latum decreases as compared to that of an uninfected one that proceeds mainly on account of irreplaceable amino acids. This changes in its turn the per cent ration between individual amino acids. Especially intensively, though not proportionally to each other, proceeds the fall of the level of lysine, arginine, histidine, threonine, valine, methionine and leucine.

In artificially reared larvae of the herring there was found the trematode Lecithaster gibbosus (Rudolphi, 1802). Of 38 investigated larvae 20 were infected. The worms become localized in the midgut. The pathogenicity of the species for larvae of the herring was established. In larvae of the White Sea herring reared under artificial conditions L. gibbosus was recorded for the first time.

The possibility of helminthoses diagnosis with the use of nonparametric models of statystic analysis was checked. The method revolves itself into the estimation of the degree of informativity of characters chosen for the description of elements of phenomena, for the isolation of a certain complex of most informative characters and the construction of a system of standards with the use of EC. The level of informativity of 38 haematological and clinical indices was tested. The indices characterizing the contents of relating to stab neutrophils and microlymphocytes in blood were found to possess the highest informativity while the contents of erythrocytes, leucocytes, eosinophiles and haemoglobin — the lesser one. Indices characterizing the contents of haemocytes, basophiles and monocytes as well as ESR possess low and average informativity. The level of identification of objects in training samplings was rather high and reached in most cases 100%.

Results of the effect of synthetic analoges of juvenile gormones of insects, dimiline, altozide and altozare, on the mite P. cuniculi have been shown. It has been noted that repeated corverings of mites in Petri dishes and rabbits' skin with 0.005 — 5% emulsions of altozide, 0.005 —10% emulsions of altozare and 0.25 — 8% suspensions of dimiline cause no changes in their morphology and metamorphosis. 1 — 4% emulsions of altozide and altozare and 2 — 8% suspensions of dimiline have been found to have an acaricid effect and cause 100 per cent mortality of mites within 48 hours.

Different behavioural experiments, including olfactometer investigations, have made it possible to show a presence of volatile substance, produced by fed females of H. asiaticum, attractive for fed males and appreciated to be a sex pheromone. Females begin to produce the pheromone after reaching the weight of 0,07 g during feeding. Hungry ticks produce no attractive substances and do not respond to the fed females' pheromone. Sticking of external openings of foveal glands brings to disappearance of attractiveness, but the latter being fully restored after removal of wax from fovea. Foveal glands so are the most possible sourse of pheromone production in the way it was shown in Dermacentor ticks (Sonenshine a. o., 1977). As a result of analysis of the data obtained to nowadays the author supposes that two types of pheromone systems (shown in the Tables of the text) are present in the limits of the Amblyomminae subfamily.

18 068 small mammals belonging to 15 species were examined. 25 059 lice of 7 species (Hoplopleura acanthopus, H. edentula, H. affinis, H. longula, Polyplax serrata, P. borealis, Neohaematopinus laeviusculus) were collected from 2355 animals of 14 species. Information is given on the species composition, occurrence and abundance of lice on shrews and rodents. 50 per cent of collected animals belong to Clethrionomys glareolus and about 85 per cent of lice — to Hoplopleura edentula. Frequent cases were recorded of the occurrence of lice on non-typical hosts as a result of interspecific contacts of animals. H. edentula was more often than other species found on non-typical hosts. No specific lice were reported from shrews and some rodents, only vole lice were found. Seasonal and age changes in lice infection rate of mass rodents as well as infection rate in years of greater and lesser abundance for C. glareolus have been studied.

During control measures taken against hypodermatosis a rapid drop of cattle infestation follows, but low warble fly populations persist, the extensity of invasion being up to 2—5%. In order to study these low populations experimentally isolated populations were established under conditions of Central Europe. Fundamental populations initiated by one gravid female H. bovis in a herd of young cattle consisted of 17, 25, 42 and 83 larvae, the extensity of infection being 11 to 52% and intensity of it 1.1 to 1.6 larvae per host. The persistence of low warble fly populations is due to an internal regulatory system limiting the population density of parasites in the host populations.

53 species of myxosporidians were recorded from fishes of Vishtynetskoye Lake of which four species (Sphaerospora galinae, Chloromyxum kovaljovae, Myxobilatus gobii, Myxobolus evdokimovae) are new. The description of the new species is given.

Troglocaridicola mrazeki sp. n. and Scutariella georgica sp. n. are described which were found on the prawn Troglocaris anophthalmus from a cave lake in western Georgia.

The relation between the stability of morphogenesis of the bream and the infection rate with ligulids has been studied. The stability of morphogenesis has been estimated by the value of coefficients of correlation between meristic characters and by the level of fluctuating asymmetry. The fishes with non-balanced morphogenesis were found to be subjected to ligulid infection to a greater extent. The stability of morphogenesis and resistance of the bream to ligulid infection can be diminished by changing the conditions of habitat — the creation of water reservoirs, pollution. The resistance of bream to ligulidoses is to a considerable extent under the check of genotype and is raised by selection during the formation of a water reservoir. Genetic approach to the problem of ligulidoses is a good supplement to the known regularities of the infection dynamics and enables its more precise predicting.

Helicometra indica Agrawal, 1964 was first found in the shelf waters of West Europe (48°22' N, 7—9°W). The infection of rey gurnard, Trigla gurnardus, with this parasite was 27%, the incidence — 1—3 specimens. A redescription of the trematode is given.

Developmental stages of trematodes of the genus Proctoeces Odhner, 1911, whose larval stages parasitize Black Sea Mytilus galloprovincialis Lam., are considered herein. Experiments were conducted on the survival of cercariae in different media (pure sea water, sea water with the addition of glucose, water enriched with metabolites of mollusks and water poor in oxygen). An attempt has been made to infect some species of crustaceans such as Idotea baltica, Gammarus olivia, Pachygrapsus marmoratus, Palaemon elegans, Mysidae gen. sp. and mollusks Hydrobia arenarum, Rissoa splendida, Nana donovani, Bittium reticulatum. Mass mortality of mussels heavily infected with cercariae of the genus Proctoeces Odhner, 1911 was observed.

Data are given on the contents of some lipoid fractions in the tissues of bullheads at various infection rates with metacercarians of trematodes C. concavum. The decrease in the lipoid contents in muscles and liver of bullheads heavily infected with metacercarians was observed. It has been established that the fraction of triglycerides is mostly affected by metacercarians of trematodes.

When studying the fauna of helminths of forest voles from the European North of the USSR a new species of nematodes, Chabaudistrongylus timani, was found in Clethrionomys rutilus Pall, and C. rufocanus Sund. Its description, figures and differential diagnosis are given.

A description and figures of a new species of nematodes found in soil on roots of Echinopanax elatum Nakai, Abies nephrolepis Maxim and Pinus koraiensis Sieb et Zucc in the Primorje territory is given. The species described differs from five known species of the genus Malenchus in body length. Morphologically the new species is close to M. machadoi from which differs in the number of cuticular rings of the cephalic area, the location of the excretory pore and size of upper cephalids.

Lysozyme excreted from the tick Ornithodoros moubata caused in vitro changes of morphological structures of the paratrachoma agent (strain LB-1).

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