Yakovlev Y. Entomopathogenic Nematodes (Nematoda: Rhabditida) in the Natural Ecosystems of Ukraine

In the dissertation work, the results of the first study of the entomopathogenic nematodes in natural ecosystems that are part of the nature reserve fund of Ukraine are presented. In general, 434 soil samples were analyzed from 23 nature reserve fund objects. In the composition of native fauna of entomopathogenic nematodes, only nematodes of the family Steinernematidae, genus Steinernema Travassos, 1927, are present, namely: S. arenarium (Artyukhovsky, 1967) (2 isolates), S. feltiae Filipjev, 1934 (10 isolates), Steinernema sp. isolate U2. Identification of entomopathogenic nematodes was conducted using combination of morphological, morphometric and molecular genetic methods. Phylogenetic analysis based on the nucleotide sequences of ITS I-5.8 S-ITS II and D2-D3 of the rDNA of S. arenarium, and ITS I-5.8 S-ITS II of S. feltiae was conducted. Dependence of distribution with geographical characteristics of research area was revealed for a set of isolates of the species S. arenarium. As a result of determined significant polymorphism of the nucleotide composition of the investigated segment of rDNA, the biogeographical interpretation of isolates' distribution of S. feltiae is not yet possible. It was revealed that entomopathogenic nematodes exhibit significant variability in almost all nominal morphometric parameters. The influence of abiotic factors on development and reproduction productivity of the species S. arenarium isolate CH in the conditions close to the natural ones were also analyzed. It was determined that changes in cultivation temperature regime significantly affected the morphometric characteristics of adult entomopathogenic nematodes, the number of invasive larvae in the evacuation from the insect corpse and led to the development of morphological anomalies of adult nematodes (the formation of "pygmy" adult individuals). This indirectly indicates changes in the nature of nematodes' nutrition under conditions of closed space and exhaustive quantity of nutrients. "Pygmy" individuals of S. arenarium ex situ were registered for the first time, and were found in situ in S. feltiae isolates.