青海湖鱼类寄生棘头虫在宿主肠中的位置选择

青海湖裸鲤和高原硬刺条鳅的肠道寄生有２种棘头虫——青海新棘吻虫和湟鱼棘头虫，在青海湖裸鲤的肠道中，湟鱼棘头虫分布在前，青海新棘吻虫在后；在条鳅肠中，２种棘头虫分布的前后关系不明显。２种棘头虫在青海湖裸鲤中共同感染时：青海新棘吻虫的位置明显后移；它们在条鳅中共同感染时：青海棘吻虫的感染强度显著下降；２种棘头虫在两宿主中的生态位重叠值都因共同感染而下降，其种间协调关系不显著。

Studies on the Site Selection of Acanthocephalan Worms of Fishes in the Intestine of Hosts in the Qinghai Lake

Gymnocypris przewalskii przewalskii (Kessler)and Nemachilus scleropterus Herzensteinare the only fish in te Qinghai Lake. Both of them are parasitized by two species ofacanthocephalans,Neoechinorhynchus qinghaiensis Liu et al.and Echinorhynchus gymnocyrii Liu etal.,which harbour in the intestine of the hosts. In the former host,E. gymnocyprii locates in theanterior section and N.qinghaiensis in the posterior section,but in the later host,the sites of twoacanthocephalan worms are not obviously different.Comparing concurrent infection with singlespecies infection,the site of N,qinghaiensis in the host G,przewalskii przewalskii moves backobviously and its intensity of infection in the host N.scleropterus decreased significantly,theniche overlaps of two parasites in two hosts decreased.The negative interspecific association oftwo acanthocephalan worms in two fishes are not significant.