中文摘要：

目的复殖吸虫是一种广泛分布的寄生性扁形动物，它们专一性地利用贝类作为第一中间宿主。自然环境中常见到一种贝类是数种吸虫的中间宿主，但该贝类的每一个体通常只存在一种吸虫幼虫期，即两种吸虫幼虫在一个螺体内具有竞争对抗现象。方法此次研究使用O．11m2框架取样器在2012年春季和秋季分别对鄱阳湖区4个不同地点的湖北钉螺种群密度、日本血吸虫和外睾吸虫的流行情况进行了调查。另外，作者还对采集到的这两种吸虫尾蚴逸出的节律性进行了研究。结果上述4个地点春、秋两季所采集到的湖北钉螺样品中，外睾吸虫的感染率（2．01％）要比日本血吸虫的感染率（O．15％）高。在春季，成活钉螺的平均密度为12．2个／0．11m2，感染率为0．3个／0．11m2；而在秋季，成活钉螺的平均密度为6．7个／0．11m2，感染率为0．2个／o．11m2。日本血吸虫尾蚴逸出的模式具有节律性，在12：00—14：00之间出现一个峰值；而外睾吸虫尾蚴逸出则呈现两个峰值：早期的峰值出现在6：00—8：00之间，晚期的峰值出现在16：00—18：00之间。结论此次实验在不同地点和不同季节所采集的湖北钉螺中，外睾吸虫相对于日本血吸虫具有较高的感染率，这对于更进一步研究湖北钉螺种群中吸虫感染的相互关系具有很重要的意义。特别是对于外睾吸虫的研究，由于其在血吸虫病的生物控制中具有很重要的作用。

英文摘要：

Digenean trematodes are a widespread group of parasitic flatworms that use snails somewhat exclusively as their first intermediate host and one species can competitively exclude other species in a single individual snail. In this study, prevalence of the trematodes, Schistosoma japonicum and Exorchis sp. , among populations of Oncomelania hupensis and pop- ulation density of the snail in four different marshland locations around Poyang Lake, China, was studied during spring （April） and autumn （October） of 2012, by using a 0.11 m2 frame sampler. Also, the rhythm of cercarial liberation of the two trema- todes from this area was investigated. Results showed that the prevalence of Exorchis sp. infection among O. hupensis popula- tions was high （2.01%）, compared to S. japonicum （0.15%） over the four investigated sites during the spring- and autumn- collected samples. The mean density of live snails in spring was 12. 2 per 0. 11 m2 with overall infection of 0. 3 snail per 0.11 m2 ; while in autumn, the mean density of live snails was 6.7 per 0.11 m2 with infection rate of 0.2 snail per 0.11 m2. Cercarial release pattern from S. japonicum was circadian, with a single peak of emergence between 12：00 and 14：00 pm, whereas that of Exorchis sp. displayed a bimodal peak of emergence： an early emergence peak between 06：00 and 08100 am, and a late emergence peak between 16：00 and 18100 pro. Finaly, the higher prevalence of Exorchis sp. infection among O. hu- pensis populations compared to S. japonicum at different sites and seasons in this study necessitates further investigation con- cerning interaction among trematode infections within O. hupensis populations, especially in regard to Exorchis sp. , due to its importance in schistosomiasis biological control.