Biocenotic relations of the invasive species Sinanodonta woodiana (lea, 1834) with native species of freshwater fauna of Ukraine.
It was studied the interspecific relationships of the invasive Chinese pond mussel Sinanodonta woodiana with native species of freshwater fauna of Ukraine (by the example it was used a pond on the Pyatygirka river, Romanivka village, Zhytomyr region). Half of the S. woodiana examined specimens (45,1%) were inhabited by symbionts. Mixed invasions were observed in 17,4% of individuals. Among these organisms, one can distinguish truly symbiotic organisms, for which the association with the host is obligatory throughout the life cycle (ciliates of the genus Conchophthirus and Trichodina, Aspidogaster conchicola), and a group of free-living organisms that, as a rule, accidentally enter the mantle cavity of the mollusk, but are capable of live there permanently (Helobdella stagnalis, larva of Chironomus sp.). The main indicators of infection of mollusks with symbionts are indicated. The pathological effect of parasites (Trichodina and Aspidogaster) on the body of the S. woodiana has not been established, which may be due to both their low prevalence and intensity of invasion in the conditions of the studied reservoir, and the low harmfulness of these parasites. The smallest occurrence of symbionts (11,1%) among age groups was recorded in 2-year-old specimens of the Chinese pond mussel, and only one symbiont was found in them - the ciliate Conchophthirus sp. Almost all symbionts described in the article are found in 3-year-old mollusks and their occurrence in this age group is 44,4%. Only the larvae of Chironomus sp. identified in 4-year-old and older individuals. The features of the formation of joint malacocenoses of invasive and native species are analyzed. After the appearance of S. woodiana in the pond, the population density of the native species Unio pictorum and Anodonta anatina decreased significantly - from 3,6 ind./m2 (in 2005) to 0,2 ind./m2 (in 2020). The analysis of such dynamics allows us to assert that the introduction of the Chinese pond mussel has a negative effect on the native unionids. Thus, the invasive species S. woodiana enters into biocenotic relationships of three types (symbiosis, neutralism, antibiosis) with representatives of different taxonomic categories and is able to significantly affect the natural biota of the aquatic habitat.