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The life cycle of the itch mite Sarcoptes scabiei (L.), an intracutaneous parasite of man and animals, has been studied. The paper concerns morphological adaptations, embryonal and postembryonal development, life cycle pattern, scabious passage as a reproductive formation, invasive stages, feeding, reproduction and topical relationships with the host, distribution and survival in the environment.

Ontogenetic allometry of exoskeleton organs has been studied on laboratory cultures of Rhipicephalus bursa and R. turanicus in groups consisting of 30 individuals. It is shown that the character of allometry in both species is described by the exponential dependence equation. Relative growth ratio differs during the 1st and 2nd moulting. Growth gradients in males and females of both species do not practically differ during the 1st moulting, while during the 2nd moulting the absolute value of relative growth ratio of organs, in males and females differs. In R. bursa and R. turanicus growth centres coincide during the 1st moulting, but in R. turanicus during the 2nd moulting the shift of growth centres takes place. Variability in relative growth ratio is close to 10%, as to individual characters, it reaches 20%. There is no correlation between the organ sizes of nymphs and imago, i.e. organ sizes at each developmental phase are not distinctly determined hereditarily. At the same time, there is observed a correlation between the sizes of organs of imago and mass of engorged nymphs. Relative growth ratio in the equation of allometry is determined hereditarily and defines the sexual dimorphism in sizes of organs, while the initial growth index depends on the degree of fatness of the individual at the previous developmental stage.

Analysis of peculiarities in organization and functioning of metabolic ways of biosinthesis of purine and pyrimidine nucleotides in representatives of Sporozoa type has shown that molecular aftereffects of adaptation to intracellular parasitism in unicellular eucaryots consists in the increase in the level of molecular organization, loss of some metabolic path ways and some enzymes, origin of a new metabolic system, a host-parasite one. Functioning of this system is achieved due to developing by the parasite mechanisms that are similar to the host's ones.

By means of spectrophotometric method there was determined the activity of three enzymes of biosynthesis of purine nucleotides: amino imidazole ribonucleotid-carboxylase (AIR-carboxylase, EC 4.1.1.21), an enzyme of biosynthesis of purine nucleotides de novo in plerocercoids of Schistocephalus pungitii and Digramma interrupta; inosine monophosphate-dehydrogenase (IMPh-dehydrogenase, EC 1.2.1.14), an enzyme of salvage path, and adenylosuccinate lyase (EC 4.3.2.2), an enzyme taking part both in biosynthesis de novo and salvage in plerocercoids of Schistocephalus pungitii. The activity of AIR-carboxylase was not determined. Specific activites of adenylosuccinate lyase and IMPh-dehydrogenase amount to (1.34±0.3) • 10-3 and (1.2±0.4) • 10-3 µmole/min • mg protein, respectively. The activity of the three enzymes was determined in the liver of ten-spined sticklback, a host of S. pungitii plerocercoids. The question of metabolic dependence of Ligulidae plerocercoids on hosts to provide for purine bases is discussed.

Nematodirus nemorhaedi sp. n. is described. The new species was found in the small intestine in three long-tailed gorals from the Primorye Territory. The species differs from other species of the genus, parasites of ungulates, by very large (over 1.5 mm) spicules and characteristic structure of their distal end in males; by long (about 1 mm) ovijector in females and by a specific combination of characters of synloph, genital bursa in males, sizes of body, structure of vulva, sizes and shape of eggs and tail in females.

The infection of the hermit crab Pagurus middendorffi, inhabiting the Vityaz Cove (the Gulf of Peter the Great), with exoparasitic abdominal isopod, Athelges japonicus, results in the parasitic castration of the host which in infected individuals is accompanied by significant morphological changes. It has been established that parasitic invasion causes the decrease in body mass of females, the increase in body mass of males, fall in the generative production and therefore in the number and biomass of the population on account of the general decrease in the number of generated eggs. At the same time the extensiveness of the infection does not depend on the host's population density. The effect of the infection on the reproductive potential of hermit crabs is assumed to be a mechanism which "insures" the population against excessive reproduction only with increasing attainability of gastropod shells necessary for hermit crabs.

Odagmia laplandica Chubareva et Yankovsky, sp. n. from the Lapland State Reserve (the Murmansk region) is described.

The first description of morphology of Hybomitra kaurii larva and pupa and redescription of H. lurida larva are given. The redescription of H. lurida larva, earlier described from North America (Teskey, 1969), is due to new requirements for the taxonomy of tabanid larvae and a greater geographic remoteness of places where the material was collected (North America and Karelia).

Ewingana (Doreyana) teniotis sp. n. is described from the free-tailed bat Tadarida teniotis (Rafinesque, 1814) captured in the south of Kirghizia (Ferghana mountain range). It is the first record of the genus Ewingana in the USSR. The females of E. (D.) teniotis sp. n. differ from all other known species of the subgenus Doreyana by the short setae d4 (15 mkm in length) and from the closely related species E. (D.) crinita Dusbabek et Lukoschus, 1971 by the short setae ic4 (139 mkm in length). The deutonymphs of the new species differ from other species of the subgenus Doreyana by the long setae l5 (146 mkm in length).

Comparative data on the effect of the method of catching rodents in tundra on the composition and quantitative indices of parasite fauna are analyzed. The catching of rodents by means of traps in the isolated areas results in 30 to 60% decrease in the indices of abundance of gamasid mites as compared to the catching of animals with dogs. The infection of dead animals with fleas is 4 times lower than that of living ones.

The description of a new species of phytopathogenic nematode, Meloidogyne chosenia sp. n., found on the roots of Chosenia arbutifolia, Filipendula camtschatica, Urtica platyphylla and Elytrigia repens in Kamchatka, is given. The species differs from close species: from M. aquatilis by the absence of terminal projection in females, a longer stylet in males, smooth cephalic end in females and larvae; from M. caraganae by long stylet and short spicules in males, structure of cephalic end and long thin tail in larvae; from M. caroliniensis by cuticle pattern of anal-vulvar area in females, shorter body length and longer tail in larvae; from M. cruciani by a more anterior position of excretory pore in females, structure of cephalic end and oesophagus in larvae.

A new species of Archigregarinida, Selenidium pennatum sp. n., from one of the White Sea polychaetes is described. S. pennatum inhabits the stomach of the sublittoral worm Flabelligera affinis. Mature trophozoites elongated and flattened on each side, up to 160 X 36 µm, with the pointed anterior and rounded posterior end. The nucleus at about the middle of the body, spherical, 14—26 µm in diameter, with a spherical nucleolus. Mature trophozoites immovable, young ones bend very seldom. Syzygy caudal, 208—230 X 29—33 µm, immovable, nuclei are not visible. In contrast to the other species of this genus Selenidium pennatum has no longitudinal pellicular striations. The ultrastructural data permit to attribute the new species to the order Archigregarinida.

In the infected turbellarians we usually found 10 to 15 orthonectids in parenchima. The females in fresh preparations are 75 to 80 µm long and 15 to 20 µm wide. The cells of the outer jacket are arranged in rings around the axial mass. Tyhe silver impregnation has shown that the jacket cells form a very stable pattern. There are usually 24 rings of jacket cells. Each ring contains almost permanent number of cells. Ten rings are not ciliated. The cells of these rings are extended in transverse direction. The cells of the other rings bear many rows of ciliae. One of the cells in ring 14 carries a genital pore. In the living material the large oocytes occupying the whole central part of the axial mass were found. The total amount of oocytes is about 22 to 24. The males in fresh preparations are about 35 µm long and 8 to 10 µm wide. As well as females, the males are covered by jacket cells which usually form 24 rings. 7 rings are not ciliated. The medium part of the axial mass is ooccupied by active spermatozoans. In the anterior one-forth of the axial mass the light vacuoles are found. The diameter of these structures is 3 to 4 µm. The details of morphology of this species permit the authors to attribute it to the genus Rhopalura and to establish a new species, R. variabili Aleksandrov, Sljusarev, sp. n.

The morphology of Proteomonas inconstans endomastigotes has been examined after their stay during 24 hours in the air. Changes occur in the surface structure, flagellum and flagellar pocket, cytoplasm, endomembrane system, mitochondrion, kenetoplast and nucleus. Considerable increase in the lipid inclusions was observed. Changes in the morphology of the investigated endomastigotes are similar in many respects to transformations that are known for the cyst formation process in the genera Leptomonas and Blastocrithidia. The obtained facts allow us to consider the endomastigotes as a special type of the transmission stages of trypanosomatides.

The accessory sclerites in one specimen of adult Encotyllabe sp. are described for the first time. They are considered to be accidental structures normally resorbed in adults of Encotyllabinae. Significance of such apomorphic feature as accessory sclerites in the evolution of capsalids and the cases of their reduction are discussed.

Summary is absent.