COMMUNITY ECOLOGY OF INTESTINAL HELMINTHS IN GYMNOCYPRIS WADDELLII FROM YAMDROK LAKE, TIBET AUTONOMOUS REGION, CHINA

This paper studies the community ecology of intestinal helminths in Gymnocypris waddellii from Yamdrok Lake, Tibet Autonomous Region, China, and the interactions among the parasite community, environmental conditions of the Tibet Plateau, and unique hosts. In July 2020, 180 samples total length: 22.20—49.20 cm; average length: (36.76±4.18) cm; weight: 77.3—896.7 g; average weight: (425.92±148.27) g, including 120 females and 60 males, were dissected for the analysis of community structure, interspecific relationship and other aspects of community ecology. Intestinal helminths in the samples consist of 5 species: Neoechinorhynchus sp., Parabreviscolex niepini, Allocreadium sp., Contracaecum eudyptulae and Streptocara sp., if ranked by the prevalence of infection from the highest to the lowest (or Parabreviscolex niepini, Neoechinorhynchus sp., Streptocara sp., Allocreadium sp. and Contracaecum eudyptulae, if ranked by the mean abundance of infection from the highest to the lowest). The Margalef index of species richness is 0.59, the Shannon-Wiener index of species diversity is 1.26, the Pielou index of species evenness is 0.83, and the Berger- Parker index of species dominance is 0.50. Parabreviscolex niepini is the dominant species. Positive correlations are found between 4 groups of species: Neoechinorhynchus sp. and Allocreadium sp.; Contracaecum eudyptulae and Neoechinorhynchus sp.; Contracaecum eudyptulae and Allocreadium sp.; Contracaecum eudyptulae and Streptocara sp., if ranked by the degree of correlation from the highest to the lowest. No interspecific association is observed between other species of parasitic worms. The number of infected hosts is over 50% of the sample size. The number of hosts infected with one parasite species is the highest, followed by the number of hosts infected with 2 parasite species. Hosts infected with 3 or 4 parasite species are less common, and there are no hosts infected with 5 parasite species. In comparison with the same parasite species in the same hosts from the adjacent Chugutso Lake, which was once connected with Yamdrok Lake in the south of Tibet Autonomous Region, intestinal helminth communities in hosts from Yamdrok Lake feature higher values of prevalence and mean abundance of infection, and different dominant species. Interspecific compatibility, a measure of interspecific association, is used to describe the coexistence or competitive exclusion between two intestinal helminth communities in the hosts from Yamdrok Lake. It’s found that the interspecific compatibility between Nceoechinorhynchus sp. and Allocreadium sp. is the highest but unstable, and it changes with the water environment and species composition in the communities. The variation in the number of hosts infected with more than one parasite species indicates that the difficulty in achieving coexistence increases when interspecific interaction grows with the increase of the number of species in a sub-community.