捕食者对长额象鼻溞形态及种群密度的影响

Effects of Predators on Morphology and Population Density of Cladoceron Bosmina longirostris

为探究在捕食者诱导下长额象鼻溞的表型形态及种群密度变化,使用近邻剑水蚤作为捕食者,长额象鼻溞作为被捕食者,设滤液组(信息素)和接触组(物理刺激)2个处理组,分析不同处理对长额象鼻溞种群数量、个体大小、钩角型占比及各形态特征的绝对长度和相对长度的影响。试验结果显示,长额象鼻溞的种群密度在接触组中略微降低(P>0.05),但在滤液组显著上升(P<0.05),较对照组增加了25.06%。2种处理下长额象鼻溞的形态均有一定变化,但近邻剑水蚤物理刺激更易使长额象鼻溞发生表型形态改变。接触组中小个体(体长300~<400μm)和大个体(体长≥400μm)等级的长额象鼻溞体长、体高、第一触角长和壳刺长的绝对长度均比对照组显著增长(P<0.05)。接触组中第一触角和壳刺的相对长度增长极显著(P<0.01),而滤液组中差异不显著(P>0.05)。接触组中钩角型个体占比有所降低,但较对照组差异不显著(P>0.05)。试验结果表明,近邻剑水蚤物理刺激更易诱导长额象鼻溞发生形态变异,但种群密度变化在信息素诱导下更显著,该结果可为水域生态系统的群落结构研究提供一定的理论数据参考。

To explore changes in phenotypic morphology and population density of cladoceron Bosmina longirost induced by predators,copepod Cyclops vicinus females and cladocerons were placed in filtrate group(pheromones)and contact group(physical stimulation).The effects of different treatment groups on the population quantity,individual size,proportion of hook angle type,and absolute and relative lengths of various morphological characteristics of cladoceron were analyzed.The results showed that the population density of the cladoceron was decreased slightly in the exposed group(P>0.05),with significant increase in the filtrate group(P<0.05)by 25.06%compared with the control group.The morphology of cladoceron changed under the two treatments,but the physical stimulation of the copepod was more likely to cause phenotypic morphology changes in the cladoceron.There were significantly higher body length,body height,absolute length of the antennule and mucrone of the small individuals(body length 300—<400μm)and large individuals(body length≥400μm)in the contact group than those in the control group(P<0.05).The relative length of the antennule and mucrone was shown to be increased significantly in the contact group(P<0.01),without significant difference in the filtrate group(P>0.05).The proportion of cornuta individuals was decreased in the contact group,without significant difference compared with the control group(P>0.05).The findings indicated that the physical stimulation of the copepod was more likely to induce phenotypic morphology variation of the cladoceron,but the population density change was more significant under predator pheromone,which can provide some theoretical data reference for the community structure research of aquatic ecosystem.