青海湖裸鲤寄生舌状绦虫的空间格局研究

STUDIES ON THE SPATIAL PATTERN OF LIGULA SP.POPULATION IN GYMNOCYPRIS PRZEWALSKIIPRZEWALSKII IN QINGHAI LAKE

舌状绦虫裂头蚴只寄生在体长小于２２０ｍｍ的青海湖裸鲤中，其种群在宿主种群中呈聚集分布。其聚集分布的强度随寄生虫种群平均密度的增加而降低。由于舌状绦虫在宿主体腔生长，产生明显的空间拥挤效应，可能导致宿主死亡或被食鱼鸟类捕食而转移到终末宿主中。在体长小于１２０ｍｍ的宿主中，密度依赖的死亡过程可能是使聚集强度降低的原因；而体长１４０－２００ｍｍ的鱼中，则是非密度依赖的全死过程使聚集强度增加．

The plerocercoids of Ligula sp.are found in Gymnocypris przewalskii przewalskii in bodylength less than 220mm in Qinghai Lake.The over-disperion of the cestode population in thefish population was observed.The degree of the overdispersion decreases with the increase ofthe mean density.The crowding effect with the growth of cestode in the cavity of the fishmight have resulted in the death of the fish.With fish less than 120mm in body length,Thedecrease may result from density-dependent mortality; where as in fish between 120-220mmin body length,the degree of aggregation increases with the decrease of the mean density onaccount of either inversely density-dependent mortality or all-or-none type mortality.