Abstract: Objective Objective To explore the sample unit size effects of spatial pattern of Oncomelania hupensis population in the marshland schistosomiasis epidemic areas. Methods Methods The push?broom method was performed to survey the snails in the study site in a basic unit size of 0.33 m×0.33 m in Poyang Lake region of Jiangxi Province. After combining different amount of survey cells，the aggregation indicators，regression models and aggregating factor index were employed to study the spatial distribution pattern. Results Results The snail population was in aggregation pattern and the smaller sampling unit could produce higher degrees of aggregation. The regression models showed that the snails distributed in the form of individual groups with attraction with each other and the aggregation was related with the snail density. The clustering factor index demonstrated that the aggregation was in? troduced by aggregating behavior habit of the snails and environmental factors，or only by snail habit itself，and the aggregating habit of snails could be expressed better by the smaller sampling unit. Conclusion Conclusion The spatial pattern of O. hupensis popula? tion in the marshland schistosomiasis epidemic areas is in aggregation pattern，and the sample unit size can affect the calcula? tion results of the related biological indices.

Key words: Oncomelania hupensis snail, Schistosomiasis, Spatial pattern, Sampling unit size effect, Aggregation, En? demic area of marshland and lake

摘要： 目的 目的 探讨钉螺空间分布格局的样点尺寸效应。方法 方法 对江西省鄱阳湖区的试验样地进行 “推扫式” 钉螺调 查， 获得试验样地以0.33 m×0.33 m为基本单元大小的连续覆盖钉螺调查数据。以不同格点数目组合为不同的假想样点 尺寸， 运用聚集度指标、 回归分析和聚集因子指数进行钉螺空间格局测定。 结果 结果 钉螺种群空间格局为聚集分布， 样点 尺寸越小越能反映出钉螺种群的空间聚集； 回归结果表明钉螺主要以个体群形式分布， 且相互吸引， 聚集强度与钉螺密 度有关； 种群聚集均数表明， 钉螺的空间聚集与钉螺习性和环境因素或钉螺自身的聚集行为等有关， 其中由生物习性导 致的聚集行为用小样点尺寸可以得到更好的测定。 结论 结论 湖沼型血吸虫病流行区钉螺空间分布格局为聚集分布， 样点 尺寸不同会影响到生物指标的测定结果。

关键词: 钉螺, 血吸虫病, 空间格局, 样点尺寸效应, 聚集性, 湖沼型流行区