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The paper describes new species of the genus Protogyrodactylus of which P. gussevi, P. solidus, P. marinoides and P. perforatus parasitize the gills of fishes of the family Theraponidae. P. alienus, P. delicatus, P. sprostonae, P. youngi, P. fissilis and P. elegantis were found on gills of members of the family Gerridae.

The fine structural organization of the ventral ganglion and the dorsal and ventral nerve cords passing in the hypodermal folds of the roundworm Ascaris suum has been studied. The ventral ganglion is composed by two clearly distinguished ultrastructural types of neurons. Organelle in the cytoplasm of the most nerve cells show distinct concentrical arrangement. The neuroplasm is rich in fiber structures which are packed in a complex circular manner. No signs of endoplasmic reticulum have been found. The characteristic feature of the central nervous system of Ascaris suum is the complete of glial cells.

Experimental infections with Trichinella pseudospiralis Garkavi have shown that white rats, mice, guinea pigs, rabbits, cats and domestic pigs are sensitive to this helminth. T. pseudospiralis is more pathogenic and invasional to white mice and guinea pigs as compared to T. spiralis (Owen, 1835). Rats and domestic pigs display a certain resistance to the infection with these helminths. In the muscles of rabbits larvae of T. pseudospiralis remain vaible a shorter period of time than larvae of other species. The possibility of T. pseudospiralis circulation in the synanthropic biocoenosis with the participation of cats, rats and pigs is not excluded.

The paper reports original data on the ontogenesis of Raphidascaris acus parasitic in predatory freshwater fishes. It should be noted a remarkably wide range in intermediate hosts belonging to different classes and even types. Comparative data on the development of insects larvae (Chironomidae, Hydrophilidae, Trichoptera), larvae and fry of fishes, tadpoles are given. The morphology of individual stages of R. acus is described. It has been established that many intermediate hosts can be at the same time reservoir ones. The possibility has been proved of passing the IIId stage larvae from one animal to another. The paper describes the circulation of Raphidascaris acus invasion in nature.

Up to now there has existed a very brief description of Ixodes eldaricus and the species has been known only from scanty collections from Dagestan, Transcaucasian republics and from a somewhat larger material from Turkmenia. A study of collections preserved in Zoological Institute, USSR Academy of Sciences, has shown that the species has a wider distribution within the above territories and occurs in Uzbekistan and Tadjikistan. The species was recorded as well from the Crimea, Kazakhstan and Kirghizia. I. eldaricus is mainly adopted to mountain forests. Larvae and nymphs parasitize both birds and small mammals, adults parasitize birds. The species displays allied connections with I. redikorzevi Ol., 1927, I. ricinus (L.), 1758 and I. gibbosus Nutt., 1916. The distribution areas of the above species and that of I. eldaricus transgress considerably. Due to schematical diagnoses the species in question is often mistaken in the literature for I. redikorzevi. In foreign literature it is known as I. tatei Arthur, 1959.

Reactions to the day length in hungry and engorged larvae and nymphs of Haemaphysalis (Kaiseriana) longicornis (parthenogenetic race from South Maritime Territory) were studied experimentally. The aggressive behaviour of both phases is regulated on the basis of a long-day reaction (in larvae at 18°, in nymphs at 18° and 25°). A long-day activation of larvae at 18° takes place in 5 to 10 days. Photoperiodic conditions of the maintenance of hungry larvae at 25° affect their metamorphosis period. Short-day larvae transformed into nymphs 2 to 3 days quicker than long-day ones. The state abequate to a new regime comes in 5 days after the transfer of larvae from a short day into a long one and in 20 days after their transfer from a long day into a short one. Engorged larvae do not respond to the changes in the photoperiod. Metamorphosis duration of nymphs does not depend on a day length.

Dissection and calculation of yellow bodies in ovaries as well as the visual examination of females for the presence or lack of the red pigment have yielded data on the physiological age and age composition of females of Culicoides sinanoensis population.

Observations were carried out in the taiga zone of the Upper Pechora in 1964. 13 species of the genus Culicoides were registered from that zone, breeding places were recorded only for 9 of them. Typification of that breeding places was done on the basis of the hydrological regime of waters and geomorpological characters of the locality. Constant water bodies are characterized by the greatest species variety (7 species). 4 species were found in the constant water bodies above flood-lands. Temporary waters of flood-lands and terraces above them differ in a poor species composition (one—two species).

The paper deals with the ways of discovery of the iodinophilous vacuole in spores of myxosporidians of the family Myxobolidae. Phase-contrast microscopy reveals the vacuole only after a certain period of time. The results of the treatment of spores of Myxobolus mülleri, M. bramae, M. dispar, M. albovi, M. exiguus, M. nemeczeki, Thelohanellus oculi-leucisci and Henneguya psorospermica with lugol, the PAS reaction and following the A.L. Shabadash method are discussed. During a spore formation the number of polysaccharides in it increases. When spores are outside of the host polysaccharides of the iodinophilous vacuole are gradually used. The iodinophilous vacuole is regarded as a depot of reserve nutrient such as glycogen in a spore. The opinion is supported on the reality of the iodinophilous vacuole as a morphological formation in spores of Myxobolidae and the necessity to use it in the systematics.

A new microsporidian species, Plistophora tabani sp. n., was recorded and described from larvae of Tabanus sp. from the mountain Turgenjriver (Zailijsky Alatau). The new species differs from all known microsporidians of gad flies in the structure of spores, moprhology of developmental stages forming during sporogeny and localization of the insect-host body. Sizes of fresh spores are 2.6—6.4X1.3—2.5 mk, those of fixed ones — 2.1—5.4X1.3—1.9 mk. The new species causes pathological and morphological changes in the inijured tissues of tabanid larvae.

A study of intraspecific variability of Coccidia is not only of theoretical importance but is also very essential in practical respect (for the elaboration of an active prophylaxis method against coccidiosis of birds information is necessary on the reproductive, virulent and immunogenic properties of strain of Coccidia from various zones). The paper presents results of studies of virulent, reproductive and immunogenic properties of 13 strains of Eimeria tenella obtained from various zones of the USSR. The investigations have shown that within the ranges the species E. tenella there are strains which differ in their virulent propertis (lethality among chickens infected with oocysts of various strains varied from 12.5 to 80%). The studied strains differ in their reproductive ability (nearly half of the strains differ in their reproductive abilities for 50% and more). Tests on the cross immunisation have shown that some strains of E. tenella differ immunologically.

After immunization of rabbits with virulent (RH) and little virulent (LEI) strains of toxoplasms the content of gamma-globulinas in sera increased over two times and simultaneously antibodies appeared recognized at first by means of the immunodiffusion reaction and then by the complement fixation test. LEI strain caused a longer hyper-globulinemia and yielded more frequent positive results of the complement fixation test in a high titre than RH strain. The comparison of precipitation lines obtained during the immunodiffusion reaction revealed differences between rabbits immunized with strains of different virulence. The separation of immune sera into fractions was done by means of gel-filtration through sefaradex G-200. The obtained fractions contained a low concentration of purified antibodies which by their electrophoretic mobility can be referred to gamma-globulins.

Gastopods of Hydrobia ulvae infected with larvae of trematodes have a lower resitance to drying and water-freshening as compared to sterile animals. The deterioration in the isolation of organisms from the environment is suggested to be one of the main reasons affecting the resistance that is proved by a high salt loss rate in infected hydrobians placed into distilled water.

Summary is absent.

Summary is absent.