COMMUNITY STRUCTURE OF THE INTESTINAL HELM INTHS OF THE CHINESEHOOKSNOUT CARP, O PSAR IICH TH YS B ID ENS(GUBNTHER), FROM THEDANJANGKOU RESERVIOR

Many parasite community structures in fish have been demonstrated non2random, but the resultswere not consistent at any time.Some environmental factors and host traits are likely to influence the parasite community structure.Here,we address this question using data on the intestinal helminthes community of the Chinese hooksnout carp Opsariichthys bidens from the Danjiangkou Reservoir, China, and focus on the impactions caused by host body length and season variation.During the time from February 2004 to November 2005, 848 specimens ofO.bidens were collected and examined. In total, 14 species of the intestinal helminths were found: 7 nematodes, 4 digeneans, 2 acanthocephalans and 1 cestode The result showed that 87.49%ofO.bidenswere parasitized by at least one parasite species and the mean intensity was 8.71±11.557.The mean infracommunity diversity was Brillouin index= 0.238±0.287.The infracommunity diversity showed significantly positive correlation with hostps total length(Spearman rank correlation coeffection rs= 0.09,pp> 0.05).The nematodes Camallanus cotti and Rhabdochona cascadilla, the cestode B othriocephalus acheilognathi, and the acanthocephalan M icracanthorhynchina motomurai with higher prevalence and intensity were the core species of this community.The infection intensities of the core specieswere significantly correlated with the host’s body length(rs= 0.238,-0.159, 0.150,-0.115;pC.cotti andR.cascadilla,R.cascadilla and M.motomurai showed significantly positive or negative correlations(pO.bidens were proved to be not random.Variation of the Spearmanps rank correlation coefficients of the intestinal helminths in seven body length groups,which was arbitrarily divided as L< 8cm, 8cm≤L< 10cm, 10cm≤L< 12cm, 12cm≤L< 14cm, 14cm≤L< 16cm, 16cm≤L<18cm,L≥18cm respectively, showed that the changes of diet and body length of the host had significant impact.The parasite community in hostwith longer body length inclined to have significantly interspecific correlation.Also the parasite community in summer and autumn show the same tendency.