B. R. Striganova

Specific features of nitrogen transformation in the gut and coprolites of earthworms

It has been found that nitrogenase activity in the guts and coprolites of three earthworm species (Lumbricus terrestris, Aporrectodea rosea, and Aporrectodea caliginosa) is one to three orders of magnitude higher than that in the control soil. In A. caliginosa earthworms, the actual nitrogenase activity remains high upon keeping them in soils of different types. However, it reaches a peak in the gut lumen and decreases to a minimum on its wall, which is evidence for a major role of transitional microflora in intestinal nitrogen fixation. Nitrogen fixation activity in freshly excreted coprolites decreases to one-half or one-third of that in the gut and then increases again, reaching a peak on days 3–5 of exposure in the soil. According to the results of multisubstrate testing, the functional diversity of nitrogen-fixing soil microorganisms increases in the course of passage through the earthworm gut. Thus, the microbial community in coprolites retains its functional potential and, within a few days, shows the second peak of activity in the soil. Due to a short-term increase in the rate of nitrogen fixation, coprolites contain a pool of bound amino acids, which become involved in the formation of new humus substances.

Genetic diversity of populations of the earthworm Lumbricus rubellus (Hoffm.) (Oligochaeta, Lumbricidae)

The genetic diversity of Lumbricus rubellus Hoffm. earthworms collected in different parts of the Moscow and Kiev regions was studied by means of electrophoresis in polyacrylamide gel, using the loci encoding unspecific esterases and generic proteins as biochemical-genetic markers. A considerable diversity of samples in all alleles of these loci was revealed. With respect to allele frequencies of the locus My1, the samples from the Moscow and Kiev regions formed two genetically distinct spatial groups. Within these groups, the samples were genetically heterogeneous, and each of them could be regarded as an individual population.

Evaluation of Production Parameters of Earthworms Eiseniella tetraedra Sav. in a Laboratory Culture

Use of earthworm Eiseniella tetraedra in vermiculture was tested for the first time. The structural parameters of its natural and laboratory populations under constant hydrothermal conditions were determined together with the production parameters such as the rate of weight gain, cocoon production, and duration of embryonic development. The mean weight gain was 84% of the baseline within 6 weeks, the rate of cocoon deposition was 0.8 per week, and the incubation duration was about 3 weeks, which provided for population doubling within 3 months. The obtained data demonstrated a good adaptation of Eiseniella tetraedra to the culture conditions with an artificial organic substrate.

Temperature as a Factor of Niche Separation in Free-Living Mesostigmatid Mites (Mesostigmata: Arachida, Parasitiformes) of Storm Detritus

We carried out a laboratory investigation of temperature effect on survival as well as reproductive and trophic activities of mesostigmatid mites. Representatives of gamasid (three species) and uropodid (two species) mites abundant in storm detritus were used as model species. The upper reproduction limit and the upper survival limit were determined for the mites and their preys in the thermal range from 29 to 47°C. Most of studied species managed to survive and propagate in a wide thermal range corresponding to the thermal gradient in the peripheral zones of algal belts. The role of temperature as a factor of ecological niche separation in saprophytic Mesostigmata and formation of polydominant mite communities in the algal belts were demonstrated.

Factors determining the origin and maintenance of redundant species diversity of the soil animal population (by a case study of the Far East)

The factors determining the origin and maintenance of a high taxonomic diversity of soil communities are discussed by a case study of the key groups constituting the soil saproblock. The bulk of the species richness in the southern Far East is localized to the coniferous-deciduous forests retaining the tertiary elements in their flora and ancient relations with the Asian tropical fauna. The roles of the following factors are considered: the long-term geographic isolation in the absence of catastrophic climate changes; pyrogenic effects, enhancing formation of isolated survival sites; and abundance of mutagenesis in various pedobiont groups. The high species richness of individual taxocenes in combination with a high topic association in the distribution of closely related and ecologically similar species suggests the absence of competitive exclusion. It has been demonstrated that this phenomenon is determined, on the one hand, by rich resource reserves and their spatial differentiation in the soil-litter stratum and, on the other, by spatial-temporal segregation and dense packing of ecological niches, decreasing competition.

Main Research Trends in Russian School of Soil Zoology (Based on the Proceedings of the IV All-Russian Conference on Soil Zoology)

In February 2005, regular IV (XIV) All-Russian Conference on Soil Zoology was held in Tyumen City by Tyumen State University. As a matter of convention, this conference bringing together nearly the whole community of Russian soil zoology summarizes recent achievements and outlines research tasks for the next years. The main trends in soil biology have been set on the basis of the proceedings of this conference and recent publications in the field.

Microbial population of the digestive tract of click beetle larvae (Elateridae, Coleoptera)

The composition and functional structure of the intestinal microflora of three wireworm species (Agriotes obscurus (L.), Selatosomus aeneus (L.), and Ampedus pomorum (Herbst)) with different dietary regimes were studied. The total abundance of the microorganisms was evaluated by fluorescent microscopy, the group composition was assessed by inoculation on a solid glucose-peptone-yeast medium, and the functional diversity was estimated by multisubstrate testing. It was noted that, in the intestine of the larvae, the total number of microorganisms was lower by 1–2 orders of magnitude than in the soil and decaying wood. It was found that the composition of the intestinal microbial communities of wireworms was radically different from that of the substrate: the Bray-Curtis coefficient did not exceed 0.25. It was found that native forms accounted for more than half of the total number of saprotrophic bacteria: in the larvae, Gram-positive cocci, enterobacteria, Vibrionaceae, Acinetobacter, and some genera of coryneform bacteria, which were absent in the soil and wood, prevailed. The micromycetes were either absent (Agriotes) or were found in insignificant quantities (Selatosomus, Ampedus). In Selatosomus, apart from the intestinal forms, representatives of Mezorhizobium, Nocardioides, and Erwinia, occurring on plant substrates, were observed.

Effects of the Vital Activity of Soil Insect Larvae on Microbial Processes in the Soil

The effects of Elateridae larvae (wireworms) on the structure, functional diversity, and tolerance of the soil microbial population in steppe ecosystems have been investigated. The trophic and locomotor activity of wireworms leads to an appreciable increase in bacterial abundance and suppression of fungal activity. The fungal hyphae in the presence of wireworms are significantly damaged, which can be related to the feeding activity of Elateridae. The increase of bacterial abundance on the background of exclusion of the fungal component shifts the microbial succession to the acceleration of organic matter mineralization. The microbial consumption of monoand oligosaccharides, alcohols, and water-soluble compounds increases in the presence of wireworms (multisubstrate test). The effect of Elateridae larvae on the microorganisms transforming nitrogen compounds is species-specific. Agriotes obscurus activity decreases their consumption of urea and creatinine by 2.1–2.5 times, and Selatosomus aeneus increases it by 1.3 and 2.5 times, respectively. The intensity of actual nitrogen fixation in the soil increases in the presence of wireworms by almost 4 times, but the losses of gaseous nitrogen do not increase because of the decrease in both the denitrification and methanogenesis rates.

Prospects of Using the Electrophoresis Technique for Identification of the Taxonomic Status of Earthworms (Lumbricidae)

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 recent trend of the biodiversity dynamic of biotic communities in forest-steppe oak forests].

Comparative studies of the structure and diversity of model biotic communities (grass cover, soil macrofauna, xylotrophic fungi and xylophilous coleopterans) were carried out in oak forests of the core and buffer zones of the Voronezh biosphere reserve. The functional structure of the communities in the buffer zone had clearly expressed nemorose features characteristic of the broad-leaved zonal forests, while that in the core zone demonstrated more xerophilous patterns with a wide participation of meadow-steppe elements. The restricted anthropogenic activity in the buffer zone enhances the mesophytization of the oak forest habitats. The complete elimination of anthropogenic pressure in the core zone for two last decades results in the formation of a peculiar, dynamic pattern of forest ecosystems, which corresponds to the zonal climatic conditions.