洞庭湖区钉螺生存状态观察

 目的 研究新时期下洞庭湖区钉螺（Oncomelania hupensis）种群动态变化规律，为制定控制钉螺繁殖扩散和血吸虫病流行策略提供依据。方法 2007年10月～2008年10月选择湖南省岳阳市君山公园靠近洞庭湖的一块草滩为现场，采用系统抽样选择和固定查螺点，每月查螺后分框记数，测量钉螺体型，压螺鉴定死活并观察生殖腺变化。首先计算各月钉螺密度、死亡率及雌雄比例，其次绘制密度、死亡率曲线并对钉螺密度进行Cox-Staurt趋势检验，做雌雄月份分布条图并进行χ²检验，电镜分析钉螺生殖腺变化情况。结果 2007年11月钉螺活螺密度最大，为11.09个/0.11 m²；2008年11月最小，为1.25个/0.11 m²；死亡率出现两次高峰，2008年2月出现最大值，为88.80%，2008年11月再次出现高值，为73.78%。Cox-Staurt趋势检验尚不能认为钉螺密度有下降趋势。雌雄构成无明显月份差异（χ²=18.14，P=0.11）；生殖腺5月份卵巢较萎缩，8月份水下卵巢极度萎缩，雄性生殖腺未发现明显变化。电镜发现大雪冰冻天气和水淹下钉螺生殖腺有明显变化。结论 湖南持续大雪冰冻天气可能对钉螺生态有一定影响。钉螺密度波动下降，观察现场钉螺种群可能处于衰退状态。

Observation on the living status of Oncomelania hupensis in Dongting Lake Area

Objective To research on the change of the Oncomelania hupensis (O. hupensis) population in the new era and to provide instrumental information for developing strategy, so as to control the O. hupensis reproduction, diffusion and schistosomiasis epidemic. Methods A bottomland close to Junshan Park in Yueyang City, Hunan Province was selected as the study field. The whole study period was from October, 2007 to October, 2008. System sampling was designed to determine the sites of investigation where all the snails were collected and the body size was measured. The number of live snails, sex composition and changes in gonad were observed by the method of dissection in the laboratory. Snail density, death rate and sex proportion of every month were first calculated; then, density and death rate bar graphs were draught, and Cox-Staurt trend test method was used to examine the snail density change. In addition, sex proportion bar graph was depicted and χ² test was used. Change of the gonad was analyzed by electron microscopy. Results Snail density was 11.09 per 0.11 m² in November 2007, which was the highest, and the lowest was 1.25 per 0.11 m² in November 2008. There were two high points of death rate, one happened in February 2008, the other was in November 2008, the number was 88.80% and 73.78%, respectively. A desending trend for snail density was not suggested by Cox-straurt trend test, the proportion of female and male had no significant difference (χ²=18.14, P=0.11).Germen of the female O. hupensis shrank in May 2008, and shrank overly in August 2008 under water, while the male O. hupensis showed no significant change. It was found that under electron microscopy the snail gonad had significant changes under snow frozen weather and in water. Conclusions The endure long period of snow weather with low temperature in Hunan province may affect the snail ecology to a certain extent, during which density of the snail decreased in most survey months, and snail populations may be in recession.