Архив выпусков

Quoting the definition of parasitism as a biological fact, the author describes range of extention of parasitism in the nature and forms of its appearance. Among zoozooparasites we can distinguish such which form large, tight systematic units (Cestoda). Studies in their philogenesis and regularity of evolution give a good deal of information concerning megaevolution of organisms including those specific for parasites. The evolution of parasitism within the compass of small systematic units (species, genus), that is macroevolution, has been illustrated by the example of Euglenoidina — parasites of intestin, eggs and larval forms of Copepoda, as well as by their complex life cycles. Considering the problem of speciation and microevolution, the author discusses exemplarly some facts such as: mutability within a species, intraspecific and infraspecific relations and struggle for life. The author introduces a thesis saying that the natural selection influences not only each partner of the system "parasite—host" but also the system itself as some biological unit.

Various small pelagic and other fishes from different regions of south-eastern Pacific were investigated. On their gills there were found numerous larvae of higher monogeneans locating on the ends of gill leaflets in peculiar swellings and reaching more or less the same stage. The comparison of these larvae with those of Pricea and Gotocotyla, found on the gills of Scomberomorus commersonii and Sawara niphonica and held to be narrowly specific parasites of these fishes, has revealed their identity. Free-living larvae of these genera were reared by the authors from the eggs of adult worms taken from the gills of the both mentioned species of fishes. It has been established as well that all the developmental stages of the both genera of monogeneans beginning from the stage corresponding to the structure of larvae described from other fishes occur generally on the gills of Sawara niphonica and Scomberomorus commersonii. It is to be noted that the species of fishes mentioned above are always infested with great numbers of adult worms belonging to the both genera and reaching some hundred specimens per one fish. Due to these data the development of members of Pricea and Gotocotyla may be presumed to proceed in the following ways: by means of a free-swimming larva (a common way) and in the presence of "intermediate" hosts. Apparently the infestation with monogeneans of Gotocotyla and Pricea may take place rather often, just when specific hosts, large predatory fishes of the family Cybiidae, feed upon various small fishes infested with great numbers of larvae which transfer to the gills of predators and reach there sexual maturity. Such complicated life cycle of higher monogeneans considerably changes the general notions on the nature of the development of the group in question and enable us to estimate the potential abilities of its spread on specific hosts in a different way.

The external layer of the coracidium of Triaenophorus noduiosus in newly hatched ("young") individuals consists of the cells containing the nuclei, endoplasmic net, mitochondria, lipid granules, etc. The surface of these cells is covered with cilia. A strong vacuolisation of the external layer results from the coracidium senescence. The ciliate layer is separated from the oncosphere by a dense membrane. No structures resembling the cuticle of the subsequent developmental phases of the worm were found on the surface of oncosphere.

The description of a new species of cestode, Polygonoporus giganticus nov. gen., nov. sp., belonging to a new genus is given. The cestode was discovered in the intestine of three sperm whales (Physeter catodon L.) caught in 1963—64 in the Antarctic. The low 12-lobbed scolex has two bothria. The anterior part of the strobila is spoonlike and has jagged edges. The strobila is about 30 m in length and 45 mm width. There are 5—14 genital systems in each of the proglottids.

In 1961—1966 in many water bodies of Kamchatka 16 species and one form of monogenetic suckers were found, of which two species are new to science, three are for the first time recorded as occurring in the USSR and eight — in Kamchatka. The monogenean fauna of the Pacific province, despite of its poorness, has happened to be somewhat reacher than it was thought before. A number of parasites (Dactylogyrus borealis, Gyrodactylus decorus, G. cernuae, G. phoxini) specific for other orders of fishes were found on one year brood of pike. At the same time in adult pikes there were found two monogenetic suckers Tetraonchus monenteron and Gyrodactylus lucii specific for this species. Evidently some monogeneans are strictly specific to the adult host and little-selective to hosts at early stages of their development.

The paper presents the results of the study of the life cycle of Echinochasmus (E.) beleocephalus (Linstow, 1837), which was nudertaken on the western shore of Hanka lake (Ussuriland). The investigation has revealed natural intermediate (Viviparus ussuriensis) and additional (Acheilognathus chankaensis, Hemiculter leucisculus, Rana temporaria) hosts of the trematode and the periods of the development of individual stages in intermediate and definitive hosts. The complete developmental cycle takes about 100 days.

No parasites were found on Cyprinus carpio haematopterus Tem. et Schl. brought from the Far East and introduced into fish ponds of the Ukraine. Only parasites characteristic of the local carp were found.

The presence or absence of the nematocyst filament cannot be used as the main diagnostic character of the class as far as the filament itself may originate convergently in different distant groups of animals. The analysis of the structure has shown that Microsporidia, in spite of the presence of the nematocyst filament in their spores, must be excluded from the class Cnidosporidia and together with Haplosporidia placed into the newly created class Plasmosporidia. The class Cnidosporidia in the new sense (subclasses Myxosporidia and Actinomyxidia) is characterized by multinuclear or multicellular vegetative stages containing nuclei or cells of two typs and multicellular spores consisting of valves, polar capsules, amoeboid embryos and other cells. The most characteristic feature of the class Plasmosporidia (with subclasses Microsporidia and Haplosporidia) — vegetative stages with several unitypical nuclei and unicellular spores possessing 1—2 nuclear sporoplasm and common membrane.

Sinergasilus lieni, brought into the USSR from China during the acclimatization of phytophagous fishes, parasitize on gill leaflets of Hypophthalmichthys harmandi (Sauvage, 1844) and Aristichthys nobilis (Rich., 1844) of all the age groups. These crustaceans are localized generally on 2-nd and 3-d gill arches, each parasite injuring 4—6 leaflets. The reproduction takes place at t 15—25° in the central part of the country and in the south but the reproduction rate and larvae survival are considerably higher in the south. S. lieni is a narrowly specific parasite. Carp, goldfish and white amur are not given to infestation.

A brief review of literary data referring generally to vectors of filariae, Protozoa and viruses is given. Plasmodia and close to them Haemosporidia are characterized by a relatively narrow range of vectors of each genus and species of a parasite (Tab. 1). In groups of filariae and especially of arboviruses each agent in majority of cases is transmitted by insects (mosquitoes in general) belonging to different genera of one family. The degree of vector susceptibility may be expressed in quantitative terms. A tendency is observed for improvement of means of quantitative expression of susceptibility degree; an example referring to filariae vectors (Tab. 2) is discussed in detail. In many cases there were found intraspecific (group and individual) differences in the degree of susceptibility. The data are analysed dealing with the genetic basis of the degree of susceptibility and with the role of gut barrier, peritrophic membrane in particular. Physiological differences of vectors are undoubtedly of great importance but they are little studied.

The most efficient technique of collecting larvae in nature is the examination of samples, taken from breeding sites, in the saturated (50%) solution of magnesium sulphate (MgSO₄). The larvae of the following 13 species of Culicoides and of one species of Leptoconops sp. were reared on the Megahead's medium: C. nubeculosus, C. riethi, C. puncticollis, C. stigma, C. circumscriptus, C. pulicaris, C. impunctatus, C. fascipennis, C. pallidicornis, C. subfascipennis affinis, C. maritimus affinis, C. obsoletus, C. saevus. The best results were obtained for the nubeculosus group. C. circumscriptus, C. pulicaris, C. fascipennis are also may be cultivated on Megahead's medium. As to C. pallidicornis, C. subfascipennis affinis, C. maritimus affinis, C. obsoletus and C. saevus only single clutches were reared on this medium. For C. impunctatus and Leptoconops sp. this medium is absolutely unsuitable. The tests were undertaken on rearing larvae on the film of Azotobacter sp. We succeeded in cultivating larvae of nubeculosus group from III stage to adults and from I to III stage, larvae of C. pulicars from I to IV stage on the powder of Azotobacter sp. Azotobacter is indispensable in rearing larvae of III and IV stages, collected in nature, to adults.

The technique of feeding of fleas through capillary with various infectious media (Hottinger's broth, defibrinated and haemolysed blood of horse, guinea pig, rat, gerbil) is described. For the tests there were used fleas (♂♂ and ♀♀) of gerbils (Xenopsylla gerbilli minax Iord and Ceratophyllus laeviceps Wagn.), mices (Leptopsylla segnis) and rats (X. cheopis). This technique allows to infect fleas with precise quantity of suspension of plague microbes of definite concentration, to observe the process of feeding of normal and infected earlier fleas, to observe the defaecation and to obtain the washes of infested faeces.

Summary is absent.

Summary is absent.

Summary is absent.