Comunities of mature helminths of moor frog Rana arvalis in the steppe zone of the Republic of Kazakhstan

Communities of five species of sexually mature helminths were studied in Rana arvalis from the Irtysh River floodplain and anthropogenic biotopes (Pavlodar, Republic of Kazakhstan), namely Rhabdias bufonis, Oswaldocruzia filiformis, Opisthioglyphe hapae, Haplometra cylindracea and Pleurogenes intermedius. The component host communities in each biotopic sample are divided into three groups of infra-communities. A little more than half of amphibians have cenoses that are formed by chance. The other two groups arise in spite of randomness: the actual frequencies and the theoretical ones, calculated in accordance with the hypothesis of random formation, differ significantly. As part of the last two groups with a high occurrence (51-62%) in amphibians from both the floodplain and the city, four are distinguished: R. bufonis + Os. filiformis, R. arvalis + O. ranae, R. bufonis + Os. filiformis + O. ranae and R. bufonis. In the floodplain biotope of R. arvalis, the basic number of R. bufonis (55.3%), Os. filiformis (48.5%) and O. ranae (60.3%). is concentrated in these complexes. In the discussed set of combinations of species in hosts from anthropogenic biotopes, the number of rhabdias is 89.8%, osvaldocruzia - 81.7%, and opistioglyph - 51.8 %. The formation of infra-communities of helminths in two different biotopic samples of R. arvalis, similar in composition, mechanism of formation, stable occurrence in space and time, placement of the leading number of individuals of R. bufonis, Os. filiformis and O. ranae in four cenoses indicates the presence of not only random, but also regular processes in R. arvalis populations. On average, in the Middle Irtysh region, two generations of R. bufonis and O. ranae and one and a half Os. filiformis are replaced during the season in the populations of R. arvalis. One generation of H. cylindracea or P. intermedius is replaced by another within two to three years. While in the host population there will be a change in one generation of haplometers or pleirogenes, rhabdias and opistioglyphs manage to change four to six, and osvaldocrusion - two or three. Parallel implementation of their development cycles by five species of helminths, different rates and number of alternating generations during the activity of the host lead to the overlap of species flows. As a result, some combinations of parasites are randomly formed. The time of infection of R. arvalis with five helminth species acts as an important reason for ordering the distribution of helminth species streams. The consequence is the non-random formation of slightly less than half of the infra- communities. If R. arvalis is the first to become infected with H. cylindracea or P. intermedius, then these trematodes restrain the development of helminths, which are populated later. This is supported by the fact that in all communities in which, together with the named flukes, R. bufonis, Os. filiformis or O. ranae parasyte, the latter have reduced number. In cases where the hosts are the first to form communities with the participation of rhabdias, ovaldocrusia, or opistioglyphs, difficulties arise for the development of haplometers and pleirogens. This is indicated by the high frequency and concentration of the leading number of individuals of R. bufonis, Os. filiformis and O. ranae in complexes that consist only of these species. This is also evidenced by the rarity of combinations in which H. cylindracea and P. intermedius are located apart or together.