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Cheyletoid mites are represented by two lineages being presumably monophyletic. The ancestor of Cheyletidae—Syringophilidae lineage probably was a predator preying on other arthropods. It is hypothesized that syringophilids originated from the common ancestor with Cheyletidae, which switched to preying in bird nests. In Cheyletidae, parasitism on birds and mammals originated independently in several phylogenetic lineages (tribes). All cheyletids are permanents ectoparasites, excluding mites of the tribe Chelonotini. In this tribe, immature instars and males are probably predators in squirrel nests. Cheyletoid lineage II is represented by exclusively permanent parasites of vertebrates belonging to three families Harpirhynchidae (Demodicidae—Psorergatidae). It is presumed from the wide distribution of these mites on birds (Harpirhynchidae) and mammals (Psorergatidae and Demodicidae), that the common ancestor of this branch could have occurred on the common ancestor of birds and mammals; however, switching during an early phase of host evolution can not be excluded. A possible reason for the absence of cheyletoids on recent reptiles (excluding snakes) involves peculiarities of their molting. The high probability of loss of mites during reptile molting seems to have prevented original establishment of cheyletoid parasites on these hosts. These mites are probably absent also on crocodilians because of their aquatic mode of life. In birds, the skin has undergone significant evolutionary changes comparable to what is seen in the integument of mammals. This probably allowed to some cheyletoid mites of the family Harpirhynchidae to transfer to intradermal parasitism in capsules similar to those induced by species of Psorergatidae. The indirect argument of the long-time parasitic relationships between vertebrates and cheyletoids serves a find of mite eggs on the dinosaur's feathers from Lower Cretaceous period (northeast Brazil) (Martill, Davis, 1998). Authors believed that these eggs were laid by feather mites (Astigmata: Psoroptidia). These rounded shape eggs, however, are more similar with those of Cheyletoidea, than with the boomerang-shape eggs of feather mites. The position of the subfamily Ophioptinae associated with snakes of the superfamily Colubroidea in the core of the family Harpirhynchidae (bird parasites) is explained by the switching of its ancestor from passerine birds. Certain snakes feed on nestlings and adult birds, and most of these preys are small passerine birds.

Historical review of the investigations of helminth fauna in amphibians from Belarus is presented. In 12 amphibian species examined by different authors 46 helminth species were found, including 29 Trematoda, 13 Nematoda, 1 Monogenea, 2 Cestoda, and 1 Acanthocephala. Original data on helminths parasitizing Amphibia in Byelorussian Polesie, by the results of long-term investigations in 1986—2004 are given. Distribution of 40 helminth species by hosts and respective infestation rates are reported.

Activities and properties of adenosine triphosphatases and glucose-6-phosphatases in microsomal fractions of cestodes Bothriocephalus scorpii were studied. The highest activity of these enzymes was observed in mitochondrial fractions. The influence of different ions and effectors is studied. The effect of 10 anthelmintic preparations on activities of the enzymes was investigated. Trichlorophen, bitionol, oxinide, G-937 and G-1028 were found to be most effective preparations for ATPases. Oxinide, bitionol, G-937, G-1028, and acemidophene were the most effective preparations for G-6-Pases.

The bacteria capable of producing the enzymes hydrolyzing carbohydrates of various degrees of complexity (from starch to sucrose) were found to be associated with the intestinal mucosa of fishes and tegument of cestodes. Presence of the bacteria displaying the sucrase activity is especially important for macroorganisms, as bacteriogenous glucose can be used by all members of the arising community. The greatest contribution to the hydrolysis of carbohydrates (both in host and parasite) is obviously made by those microorganisms which are more closely connected with the digestive-transport surfaces and are hardly removable from the intestines by peristalsis. The levels of total amylolytic activity of bacteriogenous enzymes and activity of their α-amylase under the experimental conditions are comparable to those of the enzymes involved in membrane digestion of the host and parasite, which can be evidence of the significant contribution of enzymes produced by symbiotic microflora to the digestive processes in macroorganisms.

Behavior of monogeneans of the genus Dactylogyrus under low (2—5°C) and high (28—34°C) temperatures was studied. It is established, that under extreme conditions movements of monogeneans and egg laying become more intensive. After the last egg is laid, the parasites become motionless, their bodies shrink and shorten. The motionless state in which monogeneans survive unfavorable conditions known as anabiotic or resting stage. When moved from extreme to normal conditions, dactylogyrids can leave this stage, in case the influence of unfavorable factors have not led to irreversible changes in the parasite's organism. But if such changes took place, a transversal constriction is formed on the monogenean body close to the attachment disc, where the disruption of tegument occurs. Thus, appearance of the transversal constriction can be considered a death criterion for monogeneans of the genus Dactylogyrus. It was found that immature monogeneans are more resistant to the effect of extreme temperatures in comparison with egg laying parasites.

Component communities of parasites of Phoxinus phoxinus from the Chovju River near Syktyvkar City (Komi Republic) are investigated in seasonal aspect. Material for the study has been collected in May—September 2000 from 90 host specimens of ages 0+—1+. Calculations of diversity indices and other coefficients have been made by two ways — for metazoan parasites only and for whole parasite community including protozoan species. In both these cases three states of the community have been established, 1) forming community in May—June, 2) completely formed community in the end of June—July, 3) disintegrating community in August, 4) forming community in September. Seasonal dynamics of the component communities in young minnow thus found to be different from that in adult fish hosts.

The invasion with Opisthorchis felineus (Rivolta, 1884) is known to be common in the Ob River region, West Siberia. These trematodes parasitize biliary tract of devinitive host (man or some species of animals). Other opisthorchiid species occurring in West Siberia, Metorchis bilis (Braun, 1890), has also been recorded recently as human parasite. Life cycles of both these trematodes include fish-eating mammal hosts. Eggs of O. felineus and M. bilis are very similar morphologically and can hardly be indentified. Chronic invasion with the helminthes is found to be a cause of disbolism of trace elements or high accumulation of some essential and toxic elements in the organism of definitive host. The aim of the present study was to determine concentrations of some essential and toxic elements in samples of peripheral blood and bile obtained from patients infested with Opisthorchis and/or Metorchis using instrumental neuron-activation technique. At first, all patients with microscopically confirmed opisthorchiasis (by microscopic examination of faeces and bile for the helminth eggs) were examined with serological method (ELISA) for specific anti-Opisthorchis and anti-Metorchis antibodies. Among 139 examined patients, 56.1% had specific antibodies against both Opisthorchis and Metorchis, 41.7% showed anti-Opisthorchis antibodies only, and 2.1% turn out to be seropositive for anti-Metorchis antibodies only. Of 31 elements detected in the samples of peripheral blood and bile, the concentration of nine essential and toxic elements (mercury, chromium, cesim, rubidium, lanthanum, bromine, selenium, zinc, and cobalt) in the patients with the mixt-infection of Opisthorchis and Metorchis (78 individuals) and with the Opisthorchis mono-infection (58 individuals) were significantly higher than those in healthy uninfested individuals. Among these elements, mercury and chromium showed the highest concentrations in infested patients. We suggest that the significant increase in concentrations of some toxic elements in blood and bile of patients may be associated with increased bioaccumulation of these elements in environment, especially in the local river water and fish. Moreover, concentrations of such elements as chromium, mercury, cesium, lanthanum, selenium, and zinc in blood and/or bile of the patients with mixt-infection of Opisthorchis and Metorchis were significantly higher than those in the patients with mono-infection of Opisthorchis. Accumulation of these elements in the organisms of patients was positively correlated with the number of parasites and the duration of helminth infection.

Incorrectness of some traditional morphological terms, such as cuticle, basal membrane, connective tissue fibers, etc as applied to helminthology is shown.

Summary is absent.