泾县陈村水库灌区钉螺生态学研究--钉螺生长繁殖观察

目的描述人工灌溉区钉螺生长繁殖特征,为实施生态学方法控制钉螺提供理论依据. 方法在泾县陈村水库总干渠自流灌溉区选择一斗渠为观察点,于2002年8月～2003年11月,每月进行系统抽样查螺;每月随机抽样有螺框20框,室内逐只测量钉螺螺旋数和壳体长度,镜下观察雌螺并计数螺卵;全部钉螺解剖鉴定死活.同时测量水位并收集气象资料. 结果 2003年,2～4月份活螺密度最高; 7～9月份钉螺死亡率最低;多数月份雌螺存活数量高于雄螺.雌螺含螺卵呈现明显的季节性变化,含卵雌螺数从6月份开始减少,7月时未见含卵雌螺,8月份含卵雌螺数仅占观察雌螺数的9.79%,9月份占83.82%.幼螺(螺龄＞3周)出现在6～10月,大多在6、7月份.但在2002年12月份幼螺出现1个小高峰. 结论在陈村水库自流灌溉区,钉螺的新老交替可能发生在7月份,新生钉螺发育成熟可能在9月份,而这一特征可能受年度间气温变化的影响.

STUDY ON THE ECOLOGY OF SNAILS IN CHENGCUN RESERVOIR IRRIGATION AREA OF JINGXIAN COUNTY--OBSERVATION ON THE GROWTH AND MULTIPLICATION OF SNAILS

Objective To explore the rule of growth and multiplication of snails in man made irrigation, and thus to provide evidence for snail control with ecological method. Methods A Dou ditch, in the self water flowing irrigation system of Zongganqu area in Jingxian County, was selected as a survey spot. In the place systemic survey of snails was carried out each month from August 2002 to November 2003. Each time the snails from the 20 frames, sampled at random out of all frames with snails, were given measure of the length and helix of shell, and snail eggs in each female snail were counted under microscope. All snails were anatomized to see if they were dead. The temperature and water level in the field were recorded when each survey was conducted. Results In 2003, the highest living density appeared during the period from February to April, the lowest death rates of snails were seen from July to September, and during most of a year female snails outnumbered male snails. Seasonal change in snail eggs is noticed: the female snails with snail eggs decreased in June and no female snail with snail eggs was seen in July; in August 9.79% female snails were found to have snail eggs, and in September such were with most female snails. Baby snails (more than 3 weeks old) appeared from June to October, especially from June to July. However in the December of 2002, many a baby snail appeared. Conclusion In the self water flowing irrigation area of Chencun reservoir, an old generation of snails may be replaced by a new generation in July. The new generation of snails may develop the capability of multiplication in September. All those may be influenced by yearly average temperature.