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Revision of the group of chigger mites species, closely related to Neotrombicula nagayoi (Sasa e.a., 1950) is given. Areal of N. nagayoi is probably restricted to the Far East. The majority of findings of "Neotrombicula nagayoi" on the territory of the former USSR (Southern Siberia, Kirghizia, Kazakhstan, Caucasus, East Carpathians etc.) should be attributed to N. tianshana Shao et Wen, 1984, earlier known only from the terra typica (China, East Tien Shan). N. bondari Kudryashova, 1993 and N. wendai Wen et Wu, 1984 are probable synonyms of N. tianshana. N. orestias Stekolnikov, 1994, earlier known only from the terra typica (Turkmenistan, Western Kopetdagh), is for the first time reported from Kirghizia. Diagnostic characters in the nagayoi group are considered thoroughly, key for species is proposed. Intraspecific variability in N. tianshana throughout almost whole areal of this species known up to the present time is investigated by means of computer methods of multivariate analysis. Character variance in the whole nagayoi group is also investigated. In particular, it is found out, that the geographical variability in N. tianshana is associated mainly with the lengths of setae and legs, while the size of scutum and number of idiosomal setae display first of all an individual variability. At the specific level in the nagayoi group the lengths of setae and legs has also a great importance. Such similarity of intraspecific geographical variability and character variance at the specific level indicate significant closeness of species in the nagayoi group. Study of correlations between characters in N. tianshana shows isolation of AM from other setae lengths. Earlier the similar effect was discovered by the author in the study of intraspecific variability of N. delijani Kudryashova, 1977 and in the study of character variance in the vulgaris group. It is an evidence for the suggestion, that AM able to have a special significance in taxonomy of the genus Neotrombicula.

Systematics, some morphological peculiarities and host associations of the feather mite genus Bdellorhynchus Trouessart, 1885 are briefly discussed. Two species formerly known under nomen nudum names proposed by Dubinin (1956) are described: Bdellorhynchus affinis sp.n. from the Australian Shoveller Anas rhynchotis rhynchotis and B. australis sp.n. from the Cotton Teal Nettapus coromandelianus. Descriptions are based on original materials examined by Dubinin and new collections. B. affinis is similar to B. polymorphus Trouessart, 1885 and clear differs from the latter species by males only. In all forms of males of B. affinis the genital shield is relatively short, trapezoid in form, approximately equal in length and width and the hysteronotal shield without pair of sinuous or oblique lines in area of setae d1; in heteromorph males of this species the lateral margins of subcapitulum bear the little basal processus. In all males of B. polymorphus the genital shield is elongated, its length exceeds two times its width, with ovoid posterior end, the hysteronotal shield with a pair of oblique lines near the setae d1; in heteromorph males the lateral margins of subcapitulum has no processus. B. australis is closely related to B. oxyurae Dubinin, 1956. All forms of males of B. australis are distinguished from males of B. oxyurae by slightly enlarged anterior tip of genital apodeme and by genital shield consisting of two U-shaped or bow-like fragments. Besides, in homeomorph males of B. australis the hysteronotal shield is covered with longitudinal striation. In males of B. oxyurae the anterior tip of genital apodeme is acute, the genital shield is entire and trapezoid in form; in homeomorph males hysteronotal shield is uniformly dotted. Females B. australis differ by the external spermaduct as tre little blunt processus and relatively wide dotted area of hysteronotal shield (about 100 mkm). In females of В. oxyurae the external spermaduct is represented by the short acute processus, as in other formerly known species of the genus, and the dotted area of hysteronotal shield is 60—70 mkm in width.

It is suggested, that a dissimilar geographical distribution of two flea species Xenopsilla skrjabini and X. gerbilli minax in the north-western Pribalkhash area is caused by their different responses to the moisture within burrows of their common host, the Great Gerbil Rhombomys opimus. The moisture preferring species X. skrjabini is a dominant in the Alakol landscape ecological region, where the high humidity is relatively constant within burrows. In the Karasaj region the high humidity occurs only in ome seasons and therefore both species inhabit this territory. X. g. minax is the single species confined to dry burrows of the South coastal region.

The order Amphilinidea is accepted in the frames of the class Cestodaria Monticelli, 1892 (syn. Amphilinida Dubinina, 1974). Their larvae are much similar to the lycophores of Gyrocotylidea but the postero-lateral position of nephridiopores corresponds the same in oncospheres of lower Cestoda. The class Cestodaria consists of separate branch of the ectoparasitical prestrobilar Cercomeromorphae. The ancestral amphilinids — Gyrocotyle-like worms with the holdfast on posterior end — are proposed to parasitize the gut of selachians, presumably freshwater ones. Their prestrobilar (consequently, monozoic) organisation assisted them to attain a neoteny in the body cavity of their vertebrate intermediate hosts of different systematical position after the extinction fo definite hosts in Mesozoic era. Several anatomical peculiarities of the adult amphilinids are thought to be "atavistic" as they much likely characterized the extinct gut-living phase: nerve commissure surrounding embryonic hooks and calcareous bodies. Attaining maturity in the body cavity of vertebrates, the amphilinids need no attachment organs — neither on the posterior (as Monogenea and Gyrocotylidea) nor on anterior (as Cestoda) end. The latter fact may explain the similarity of Amphilinidea and mature segments of some hyperapolytic tetraphyllidean Cestodes (Trilocularia, Potamotrygonocestus) in the position of gonads and gonoducts (except uterus). The function of embryonic hooks has been changed in amphilinids as in cestodes: they serve here only for the penetration into the body cavity of the I (invertebrate) host. New function explains modifications in a hook morphology. Dubinina (1982) considered amphilinids as specific parasites of Crustaceans which included vertebrate hosts in their life cycles secondarily, but this hypothesis remains conjectural.

The morphology of the tegument of invasive cercariae and metacercariae of Diplostomum chromatophorum at different intervals after the penetration into the experimental intermediate host Cyprinus carpio (1, 3, 5, 6, 7, 10, 12, 20, 34, 40, 49 days) has been investigated. The developmental changes observed in epidermis of metacercariae are divided into three consecutive stages. At the first short stage the tegument and associated structures resemble in general those described for cercariae. Dense glycocalyx noted at this stage is proposed to protect parasites from the host's immune response. The second stage coincides with the period of intensive growth and development of metacercariae. During this time the tegument is seemingly involved in the nutrient absorption. Its free sufrace area is elevated by long numerous microvilii, the basal membrane forms frequent deep invaginations, the number of mitochondriae is noticeably increased. On this background the process of intensive local reorganization of surface structures was observed. At the third stage the tegument acquires the main features of adult worm epidermis. The well developed filamentous glycocalyx appears on its surface again.

Influence of temperature and salinity on a survival of free-living cercariae of marine littoral trematodes Cryptocotyle sp., Levinseniella brachysoma and Maritrema subdolum has been studied. The cercariae used in experiments were released from the infected mud-snail Hydrobia ulvae collected at the White Sea. It was estimated that the life span of the cercariae depended strongly from abiotic factors mentioned above. High resistence against an extremely low and high salinity was recorded for the larvae of all three species. Interspecific differences in the life span of cercariae are explained by the features in their morphology and behaviour.

The goal of the present work is to examine the effect produced by the microsporidian Nosema grylli (Microspora, Nosematidae) on carboxylesterases' complex in the fat body (the site of parasite location), and in the haemolymph of the Gryllus bimaculatus (Orthoptera, Gryllidae). The simultaneous study of the influence of another intracellular parasite of the cricket adypocytes — a coccidian Adelina grylli has been performed to compare the effect produced by two parasites. Carboxylesterase (CEs) (EC 3.1.1.1.—3.1.1.5.) form a group of enzymes, hydrolyzing the eithers of carbonic acids. The identification of the separate enzymes inside the group is hardly possible due to their overlapping substrate and inhibitory specificity (Choudhury, 1972). CEs are believed to play an important regulatory role in the key physiological processes in insects: in lipid metabolism, vitellogenesis, reproduction and others (Lands, 1965; Hooper, Wan, 1966; Bonning e. a., 1997). CEs from insect haemolymph, so called JH esterase, participate in the degradation of juvenile hormone (JH) (Hammock, 1985; Hoffmann e. a., 1994; Vermunt e. a., 1997; Woodring, Hoffmann, 1997; Paterson, Weaver, 1997). CE activity correlates with the insect ability to detoxification (Oppendorth, 1985; Ishaaya, 1993). Investigation of CEs activities during the microsporidiosis is of interest mainly for the following reasons. 1) CEs actively participate in the hydrolysis of triacylglycerids — the main storage lipids in Insects. Thus, the study of the effect produced by the anaerobic microsporidians (M) and aerobic coccidians on the activity of CEs in host tissues might be helpful in understanding the mechanisms of pathogenesis of each pathogen (Долгих и др., 1996; Паскерова и др., 1998). 2) Taking in account the role of CEs in JH III titer regulation (Khlebodarova e. a., 1996) and since it was shown that M influence on the host hormonal status similar to JH (Fischer, Sonborn, 1962; Issi, 1986), it was important to assess the influence of M on the enzyme activities. Studies were performed on the laboratory culture of Gryllus bimaculatus. Crickets were infected perorally with the suspension of spores added to the drinking water as described elsewhere (Dolgikh e. a., 1997). Crickets spontaneously infected with Adelina grylli, were used in the experiments. Haemolymph (20—50 µl) individually taken, was collected in the tubes, containing anticoagulating solution (0.1 M NaOH, 0.15 M NaCl, 0.017 EDTA, 0.04 M citric acid), and was centrifuged 5 min at 500—1000 G. Supernatant was used for the spectrophotometry and electrophoresis. The sediment containing haemocytes, after washing in 0.1 M PBS, was put on slides and incubated 15—20 min at RT in moisture chambers. The adhered haemocytes were fixed in paraformaldehyde— glutaraldehyde mixture and incubated 30 min in the reactive solution (0.5 mg/l α-naphtylacetate and 0.5 mg/l blue RR stain (Reanal) in 0.1 PBS). Slides with stained monolayers of haemocytes were studied in the light microscope (fig. 1, 2). Activities of esterases, separated by gel-electrophoresis were studied in the fat body and haemolymph of the 3—5 days old males and females or of the last (6-th) instar larvae. Samples were mixed with the equal volume of 40% sucrose and 1% Triton X-100 in PBS. After electrophoresis gels were incubated in the solution, containing 0.56% α-naphtylacetate in 0.2 M PBS (pH 7.0), 2% acetone and 0.2 mg/l blue RR stain in в 0,1 PBS (Sula, Weida, 1983). Spectrophotometrical study of esterase activities was performed in haemolymph deprived of haemocytes according Asperen (1962). Solution of 0.03 M α-naphtylacetate in 0.04 M PBS was used as a substrate. Enzyme activities was detected by the color reaction with blue RR stain. Optical density was measured with the help of spectrophotometer SP-46 at wavelength 600 nm. The obtained results (fig. 1—4; table) point to the inhibition of the esterase activities in all studied tissues while microsporidiosis. Infection of the cricket with a coccidian A. grylli did not cause the fall in the enzyme activity, on the contrary it enhance activities of some of forms of the enzyme. The CEs activities could decrease due to unspecific fall of general metabolism on the acute phase of the disease, though this assumption is in contradiction to the data obtained for other enzymes, which activities essentially increase while microsporidiosis (Долгих и др., 1996; Долгих, 1998). Microsporidians may secrete a factor suppressing host hydrolases, including those, participating in the insect defense reactions esterase activities, like some of entomopathogenic bacteria, nematodes and parasitic hymenopterans (Глупов, Бахвалов, 1998). A peptide, specifically inhibiting JH esterase activities, has been isolated from haemolymph of Pseudolitia separata larvae infected with Apantheles kariyai (Hayahava, 1990). Our previous cytochemical studies showed that microsporidiosis caused the suppressing of acid phosphatase activity (Sokolova, Issi, 1990). Besides, EM analysis revealed numerous vesicles associated with a parasite's plasmalemma suggesting high secretory activity of the microsporidian prespore stages (Соколова и др., 1994). Activities of fat body CEs have to play an essential role in a regulation of the lipid metabolism. An increase of the enzyme activity after the infection with Adelina grylli is presumably connected with a rapid utilization of triacylglycerids in the course of infection (Паскерова и др., 1998). The observed "juvenilization" of the microsporidian infected insects indicating putative enhancement of JH titer, might be considered as a consequence of the fall of the JH esterase activity. Isolation of the specific JH esterases and analysis of the alterations in their activities due to infection with the pathogens is the next spet of the research. Supported by RFBR: 97-04-48383, 96-04-48985 and "Integracia" K—0955.

Summary is absent.