群体密度对中华倒刺鲃幼鱼数量辨别力的影响

The Effect of Shoal Density on Numerical Discrimination of Juvenile Qingbo

【目的】考察单尾中华倒刺鲃(Spinibarbus sinensis)幼鱼对不同数量比的两个刺激鱼群的偏好以及该偏好是否受群体密度的影响。【方法】利用该鱼倾向加入较大群体的行为习性,采用自行设计的鱼类行为观测装置,通过改变仪器两端的刺激鱼群(Stimulus shoal)的数量以及密度大小,进行二元选择(Binary choice test)实验,计算目标实验鱼对两刺激鱼群的选择率。【结果】在密度相同的条件下,当数量比为1212,126或66时,目标实验鱼对两刺激鱼群的偏好没有统计学意义上的差异。在密度不同的条件下,当数量比为1212和126时,目标实验鱼偏好高密度刺激鱼群;然而当数量比为66时,目标实验鱼对两刺激鱼群的偏好没有统计学意义上的差异。【结论】中华倒刺鲃不能单独通过离散型数量信息(刺激鱼群的个体数)辨别鱼群的大小;当刺激鱼群的个体数较少而实验装置的刺激区空间较大时,两刺激鱼群之间的密度差异可能达不到中华倒刺鲃连续型数量信息(密度)辨别的阈值;中华倒刺鲃幼鱼可能采取了模拟数量的机制处理大数量信息而使用了对象文件系统机制处理小数量信息。

[Purposes]Qingbo（Spinibarbus sinensis）,a highly gregarious cyprinid species,was selected as experimental animals to explore the effect of population density and numerical rate on the selection rate of tested fish species on different stimulus shoals.[Methods]The numerical acuity of juvenile qingbo were measured by a binary choice test and selection accuracy was evaluated by proportion of time that focus fish stayed near one stimulus shoal versus another stimulus shoal.[Findings]The results showed that regardless of the number ratio（1212,126 or 66）,the focal fish have no preference for either stimulus shoal when measured under the same density conditions.However,under the different stimulus shoal density conditions,when the number ratio was 1212 or 126,the focal fish preferred to shoal with the denser stimulus shoal;whereas,when the number ratio was 66,the preference of focal fish was vanished.[Conclusions]It suggests that qingbo could not discriminate the difference between the two stimulus shoals solely by the discrete quantities information.The focal fish might not discriminate the density difference between two stimulus shoals when in condition of low shoal number with large hold space.In addition,it is likely that the qingbo discriminate the size difference between two big shoals by the‘analogue number system＇whereas it discriminate the size difference between small shoals with‘object-file system＇.