Grazer-induced changes in the desmid Staurastrum
Grazer-induced changes in the desmid Staurastrum
复制标题
放牧者引起的硬粒Staurastrum的变化
作者：
K. Wiltshire;M. Boersma;B. Meyer
在水生环境中，捕食者凯洛蒙已被证明影响被捕食物种的形态。过去关于浮游动物和浮游植物之间相互作用的工作主要是基于水蚤-场景模型。球藻属的藻类可以产生粘液，导致细胞聚集并从水柱中沉淀出来。这些块状物太大了，不能被达夫尼虫吃掉。因此，我们假设这可能是一种放牧防御。我们研究了大型水蚤是否诱导柱状藻中粘液球的形成，这种情况是如何发生的，以及团块的形成是否抑制了幼体的生长。用8个Staurastum菌株来检测粘液排出是由水蚤存在还是由大型水蚤分泌的化学物质引起的。所有菌株都不能单独对水蚤的存在产生反应，必须有动物在场才能诱导结块。机械作用(轻轻搅拌)导致相同的应变结块。然后对丛生的生态相关性进行了研究。用不同的Staurastum菌株作为食物，对透明水蚤(Daphnia Hyalina)幼体的生态密度进行了生长试验。当在高密度的实验中观察到大型水蚤时，这些小的水蚤不会引起同样的结块。我们观察到幼虫在细胞大小较大的品系上生长得不太好。
In aquatic environments, predator kairomones have been shown to affect morphology of prey species. Past work on the interaction between zooplankton and phytoplankton was based mainly on the Daphnia–Scenedesmus model. Algae of the genus Staurastrum can produce mucilage, causing cell clumping and settling out of the water column. These clumps are too large to be eaten by daphniids. Thus, we hypothesised that this may be a grazer defence. We investigated whether Daphnia magna induces the formation of mucus globules in Staurastrum, how this occurs, and if the formation of clumps inhibits growth in juvenile Daphnia. Eight strains of Staurastrum were used to check whether mucus extrusion is induced by the presence of Daphniaor possibly by a chemical excreted by Daphnia magna. None of the strains reacted to the presence of Daphnia water alone, animals had to be present to induce clumping. Mechanical action (gentle stirring) caused the same strains to clump. The ecological relevance of clumping was then investigated. The different Staurastrum strains were used as food in a growth experiment with ecologically relevant densities of neonates of Daphnia hyalina. These small daphniids did not cause the same clumping observed for Daphnia magna when present in experiments at high densities. We observed that juvenile daphniids grew less well on strains with larger cell size.