河湖洲滩是血吸虫唯一中间宿主———钉螺的主要分布区域。洲滩钉螺垂向迁徙与水位密切相关，但一般滞后于水位变化，以往研究没有考虑这一滞后现象，难以准确把握钉螺垂向迁徙规律。为了准确预测洲滩生境条件变化后钉螺的垂向分布高程，对钉螺迁徙过程进行概化，推导了水位变化后钉螺理论分布高程的计算模型，揭示了钉螺随水位变化的迁徙规律。研究结果表明：①钉螺分布高程随着水位增加而增加，随水位降低而降低；②水位上升时钉螺分布高程与水位之间距离有减小趋势，水位下降时钉螺分布高程与水位之间距离有增加趋势。利用洞庭湖区东口洲滩实测资料进行检验，结果表明基于滞后响应原理的钉螺垂向迁徙预测模型能够较准确地预测洲滩水位变化后密螺线的分布高程。%As the only intermediate host of schistosome , snails generally live at the bottomland of lakes .The vertical migration of snails on the bottomland is closely related to the water level but usually delayed to the water level alter -ation, which has not yet been considered in previous studies .As a result, the snails’ vertical migration is always difficult to describe or predict accurately .A generalized model for the changes of snails ’ vertical distribution was proposed in this study , and a calculation method is developed for predicting the theoretical distribution elevation of snails in the presence of altered water level .The calculation method reveals that:1) .the elevation at which snails are distributed increases with the rise of water level and decreases with the decline of water level ;2) .the distance between the snail distribution elevation and the water level decreases with the rising of water level, and increases n with the descending of water level .According to the field data at the Dongkou bottomland of Dongting Lake , the calculation method based on the delayed response for predicting the snails ’ distribution elevation was tested , and the results showed that the relationship between the snails ’ vertical distribution and the water level alteration estab-lished in this paper can be used to accurately predict the snails ’ distribution elevation .
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