Search

The population of soil mesofauna in the basin of the small river subzone of the northern taiga (Karelia) has been investigated. It was shown that indexes of the number and mass of soil mesofauna in the landscape-ecological row ofbiogeocenosises are maximal in floodplain soils. The taxonomic composition and structure of domination of the soil mesofauna population depends on the location of biogeocenosis in the landscape: earthworms are dominants in riverine floodplain biogeocenosises, and larvae of elaterids and spiders prevail in the places outside of floodplains. The abundance of saprophytic invertebrates in floodplain biogeocenosises results in formation of humus of the mull type. A group of animals with mixed type of nutrition dominates in the places outside of floodplain soils that are related with humus of the moder-mor type. The population of rove beetles (Staphylinidae) allows the division of biogeocenosises into two groups according to their position in the landscape.

The polyacrylamide gel electrophoresis technique was used for comparison of common protein of body wall tissues in five species of Lumbricidae (Eisenia nordenskioldi, E.fetida, Lumbricus rubellus, Aporrectodea caliginosa, A. longa). The statistic processing of indexes of electrophoretic similarity revealed three levels of similarity: intraspecies, interspecies, and intergenus. It was discovered that the similarity of E. nordenskioldi and E.fetida proteins corresponded to the intergenus level. The use of this method for determination of the earthworm's taxonomic status is discussed.

The distribution of polyploid races of earthworms in the East European plain and Siberia was analyzed. Amphimictic autopolyploid races of two species of the Asian genus Eisenia, E. nordenskioldi and A. atlavinyteae, are widespread in Siberia, from its southern boundary to the arctic region, while polyploid Lumbricidae in the East-European plain, except for the Volga region, are represented mainly by parthenogenetic forms of other genera. This is presumably related to differences in the Pleistocene environmental history between the two adjacent geographic regions of Eurasia.

Phylogenetic relationships within the class Clitellata were examined using nucleotide sequences of nuclear 18S ribosomal RNA gene fragments. In the analysis, the already determined sequences for the individual species representing the class members Hirudinea, Acanthobdellida, Branchiobdellida, and Oligochaeta were included. Furthermore, newly determined sequences of the thirteen representatives of the family Lumbriculidae. including 12 Baikalian endemic species, were analyzed. The hypothesis on the close relatedness of these four groups of Clitellata was supported. Leeches, branchiobdellidans, and lumbriculides form three independent parallel branches of evolution. These results were consistent with the hypothesis on the role of the family Lumbriculidae as a connecting link, or the transition form between the parasitic and free-living groups of Clitellata. At the same time, these data refute the suggestion that Lumbriculidae could be the ancestral lineage of other Oligochaeta. Moreover, polymorphic group of Baikalian lumbriculides clustered independently from the other representatives of the family, pointing to the uniqueness of the Baikalian fauna of oligochaetes, which was formed within relatively closed system of this ancient lake.

Polyacrylamide gel electrophoresis was used to study the allelic frequency distribution of four polymorphic loci (Pox, Lap, Pgm, and Odh) in 22 samples of Eisenia foetida (Sav.) from distant parts of the range: European Russia, Ukraine, Kazakhstan, and Kyrgyzstan. A hierarchical population structure was demonstrated for this species: local populations are integrated into spatial groups. Statistical analysis of morphological variation demonstrated that recognition of the spatial groups on the basis of biochemical and genetic characters as individual taxa of any rank is not justified.

The results of studying nitrogen fixation in organic substrates processed by different ecological groups of earthworms suggest that the earthworms Aporrectoidea caliginosa actively stimulate nonsymbiotic nitrogen fixation. In this respect, they exceed the manure worms Eizenia foetida tens of times due to the formation in the organic substrate of conditions favorable for the nitrogen fixing bacteria, and namely: low content of nitrogen easily accessible for microorganisms, changes in the structure of the microbial community of the substrate in favor of non-spore forms of bacteria, and suppression of the growth of saprophyte bacilli, the main competitors of nitrogen fixing bacteria for carbon nourishment sources.