THE MAIN DIRECTIONS OF RESEARCHES

The head of Laboratory
Yu.Yu. Dgebuadze

Material collection in the upper reaches of the river Tola, Mongolia

• Developmental biology and evolution of living systems
• Ecology of organisms and communities
• Biological diversity

The principal researches were centered in the course of two subjects – the study of morphology, systematics, zoogeography, ecology and evolution of Cladocera crustaceans (Crustacea, Cladocera) – one of the basic groups of continental waterbody invertebrates and the study of the ecosystem of the model natural waterbody of Lake Glubokoe (Ruza Region of the Moscow Area). General leadership in the program of long-term studies at the Hydrobiological station "Glubokoe Lake" was also undertaken.

For 10 years under report, systematical revisions of representatives of all families of Cladocera, especially of such as Sididae, Holopediidae, Chydoridae, Macrothricidae, Daphniidae, Bosminidae of the world fauna were carried out. In total, 112 species were subjected to detailed revision, 89 species were re-described with the use of new material and new characters accounting, 47 species were described as new ones for science. Inventory taking of the species diversity for Cladocera of the world fauna, totaling at present 620 species, many of which need further investigations, was undertaken. Two latest years a special attention was paid to Cladocera of Russian fauna, expeditions to the region of the South Ural and to the south of Western Siberia were organized for collection of additional material. Preliminary study of this material revealed many interesting factors. On the basis of the studies undertaken, it is suggested to publish a new monograph in future – guide book on Cladocera of Russia.

From completed in 1997-2006 systematical revisions, two studies touching upon Cladocera of the world fauna order of Ctenopoda and of the world fauna family of Ilyocryptidae should be emphasized.

Both of them are presented in the form of published monographs of sizable volume, and besides the questions on systematics they describe and generalize all known data on morphology, ecology and zoogeography of the given groups.

Absolutely new and original theme has become the problem of the study of fossil Cladocera, which up to date were not quite known and are practically studied nowhere more. It turned out that representatives of the group referred to very ancient animals, their remains were found in the strata of the lower Jura. New taxa of the rank from species to order were described for the fossils of Cladocera.

The studies of embryogenesis in Cladocera were perfectly original in their approaches and methods. Representatives of three orders – Ctenopoda, Anomopoda and Haplopoda were studied. The appearance and chronological development of all morphological and some anatomical structures were described in detail. The growth rate for the embryos at different phases of development was determined. New schemes of embryogenesis were suggested, which took into account not only the changes in morphology, but also the consequence of release from egg membranes and embryonic molts.

The whole block of data obtained on morphology, embryology and paleontology allow new approach to the development of phylogeny and evolutionary history for the given group as well as for the representatives of the entire class of crustaceans of Branchiopoda.

Material collection on ichthyofauna of little rivers, the river Ero, Mongolia

The studies of consequences of beavers reintroduction into their habitats after their long-term absence is one of the directions of the group's research

A new concept on the formation of the world fauna of Cladocera crustaceans (Crustacea: Cladocera), one of the main groups of invertebrate animals in continental waterbodies, was developed and published. This concept was based on analysis and generalization of large number of data on paleontology and zoogeography of the group and comparison of these data with the data on some other well studied groups of ancient primary aquatic invertebrates. It is proved that Cladocera as a whole are relic organisms and differed by markedly greater variety in the last geological epochs, only some of their modern representatives can be characterized as evolutionary young and developing. It is also shown that the most diversified fauna of the given group is presented in the southern-moderate and subtropical regions of the northern and southern hemispheres, while in boreal areas and tropics it is comparatively depleted. It is suggested that the offered scheme of faunogenesis can be sufficiently universal and applicable for description of fauna development for a large range of other groups of land waterbody invertebrates.

As a result of monitoring studies on pelagic and littoral zooplankton of Glubokoe Lake, the data on the changes of species composition, population structure and number dynamics of individual representatives along with the data on dynamics of several limnological and hydrochemical parameters were obtained. General long-term dynamics of community shows the signs of the tendency to cycle, which is possibly connected with climatic factors first of all. Zooplanktonic community of the lake continues to stay at the phase of long-term structural readjustment, which follows the invasion of a new mass species Daphnia galeata. This invasion has caused formation of hybrid populations and complication of the community structure. Observations made for littoral zooplankton revealed similar tendencies to cycle, and also the presence of not mentioned here previously rare ephemeral species (Daphnia magna, Pleuroxus pigroides).

Analysis of long-term data on fish populations of the waterbodies in the Selenga River basin showed that substantial climatic and anthropogenic changes (warming, eutrophication, pollution, change in the flow of the rivers) occurred within recent 20 years, led to the shifts in the ratio of ecological forms, increase in pathologies number, lowering in the local diversity and growth rate in fishes; for the first time, fish populations of the little flood-land lakes of the basin were described. The data obtained allowed the suggestion of first-priority measures on conservation of unique natural ecosystems of the Selenga basin.

The species composition of the loaches of the genus Orthrias was revised. Diagnosis of the genus and species, detailed species descriptions including osteologic ones were composed; morphological characters were illustrated in details; the maps of the ranges and the guide for species determination were drawn. Phylogenetic relations of the Orthrias and evolutionary history of this genus were discussed. Two new species were described. It has been shown that modern fauna of the loaches in Mongolia has appeared not long ago and today is at formation stage.

By the method of simulation with the use of parameters of Cladocera populations, it was determined that in the absence of predator the invasion of new species into zooplanktonic community was hampered, and in its presence the number of co-existing species increased markedly. This regularity is right only at high levels of resource reproduction (5.22).

The materials on dimensional and age composition, variation in growth and life cycles for invasion populations of common kilka Clupeonella cultriventris in reservoirs of the Upper Volga were generalized and analyzed. It was shown that common kilka in the Upper Volga reservoirs had rapider growth, earlier maturation and lesser diameter of eggs compared to native populations. It was established that common kilka had inserted into the ecosystems of the Upper Volga reservoirs, changed the structure of pelagic communities and influenced the number and biomass of local pelagic fish populations (5.22).