Stylet nematode fauna in brown soil of Bolshoi Pelis Island (Sea of Japan, Peter the Great Gulf)

The article studies the stylet nematode fauna in brown soil of Bolshoi Pelis Island (Sea ofJapan, Peter the Great Gulf) and discloses the connection between the fauna and the variation of soil ecology conditions within the island.For this, we made a soil ecology study of Bolshoi Pelis Island: we examined conditions of insular brown soil formation as well asits morphological structure and physical and chemical properties. Simultaneously, we studied stylet nematodes, found in the rootinhabitedlayer of soil: we singled out most numerous and wide-spread species, studied species distribution in connection with soil ecologyconditions, defined the systematic location of stylet nematodes, and described morphology of dangerous root parasites. The studyshows that the majority of stylet nematodes (17 species) inhabit dark humus-illuvial brown soil, while typical brown soils under humidoak forests harbour 11 species, and the ones under arid oak forests harbour only 5 species. Cocoon-forming nematodes of Heteroderasp. were found in every test-pit sample. Most of them were registered in brown soils under arid oak forests (9 males and 6 larvae), whilethe other soils house only Heterodera larvae. Some mass species such as Helicotylenchus sp. and Boleodorus rapsus were found in typicalbrown soils under humid oak forests and in dark humus-illuvial brown soils under Gmelins wormwood shrubs. Thus, most diverseand numerous nematodes inhabit dark humus-illuvial soils under Gmelins wormwood shrubs. As for typical brown soils under humidoak forests, they house such mass species as Crossnema coronatum, Xenocriconemella sp., Ditylenchus intermedius, Tylenchus hamatus,and T. criniformicaudatus (only females of all the species were found). Typical brown soils under arid oak forests present fewnematode specimens. Among the mentioned species, several pathogenic forms, such as Heterodera sp., Crossnema coronatum, Xenocriconemellasp., are of most interest. It was discovered that diversity of the stylet nematode fauna depends on the degree of comfort thatsoil ecology conditions offer for nematode existence and procreation. Species diversity and numbers grow with the increase of brownsoil humidity and humus-accumulative horizon depth.

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