Inducible anti-fish defenses in Daphnia: DVM-induction by 5α-cyprinol sulfate under quasi-natural conditions and identification of the life-history changes inducing kairomone

水蚤的诱导性抗鱼防御：准自然条件下 5α-鲤醇硫酸盐的 DVM 诱导以及诱导利它素的生活史变化的鉴定

• 批准号: 442030826
• 负责人: Professor Dr. Eric von Elert, Ph.D.
• 金额: --
• 依托单位: Arbeitsgruppe Aquatische chemische Ökologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/442030826?language=en
• 关键词: Inducible; anti; fish; defenses; Daphnia

Microcrustaceans of the genus Daphnia play a key role in lakes and ponds, as they are major consumers of planktonic primary producers and are important prey for higher trophic levels. Daphnia have become text book examples for the induction of defenses by kairomones released by predators. In response to kairomones released by fish, the major predator of daphnids, Daphnia deploy anti-predator defenses as life-history changes (LHCs) and diel vertical migration behavior (DVM), which reduce the efficiency of the predator and impact many other ecosystem-wide processes. We have recently identified the DVM-inducing kairomone released by fish to be 5α-cyprinol sulfate (5α-CPS) and determined that it induces DVM in Daphnia magna in an indoor-setup at picomolar concentrations. Methods for the preparative purification of 5α-CPS and for the quantification of 5α-CPS by ultra-high-pressure liquid chromatograph coupled to a high-resolution mass spectrometer are well established in the group.Building on this earlier work I here propose to apply 5α-CPS for DVM-induction in mesocosm experiments with a natural Daphnia community and in parallel to determine in-situ concentrations of 5α-CPS with the aim to establish threshold concentrations for DVM-induction under quasi-natural conditions. In nature, in-situ concentrations of 5α-CPS are the result of release by fish and simultaneous bacterial degradation. To account for both processes I propose to determine at different temperatures release rates of 5α-CPS of individual fish differing in size and feeding status. Bacterial degradation rates at different temperatures will be established by incubating lake water that has been spiked with known concentrations of 5α-CPS and by quantifying 5α-CPS over time. Besides DVM, life-history changes (LHCs) are another very important inducible defense against fish in Daphnia. However, the LHC-inducing kairomone is not known yet. Here I propose as the most straightforward approach to test, if 5α-CPS induces LHCs. If not, extract of fish incubation water will be subjected to bioassay-guided purification in several rounds of increasing purification by HPLC coupled to a high-resolution mass spectrometer. Fractions produced by HPLC will be tested in well-established bioassays for LHCs. Subsequent non-targeted metabolomics and fragmentation experiments will aim at identification of the kairomone. The overall aim is to (i) more precisely understand DVM-induction in Daphnia by 5α-CPS under quasi-natural conditions and to estimate production and degredation rates of 5α-CPS and (ii) to identify the LHC-inducing fish kairomone.

水蚤属的微甲壳动物在湖泊和池塘中起着关键作用，因为它们是浮游初级生产者的主要消费者，并且是较高营养水平的重要猎物。水蚤已经成为教科书的例子，说明捕食者释放的利它素诱导防御。水蚤对鱼类释放的利它素的反应表现为生活史变化（LHC）和昼夜垂直迁移行为（DVM），从而降低捕食者的捕食效率并影响许多其他生态系统过程。我们最近确定了鱼类释放的DVM诱导利它素是5α-硫酸鲤鱼醇（5α-CPS），并确定它在皮摩尔浓度的室内设置中诱导大型蚤的DVM。在此基础上，我提出了将5 α-CPS应用于自然水蚤群落围隔实验中的DVM诱导，并平行测定5α-CPS的原位浓度。CPS的目的是建立准自然条件下DVM诱导的阈值浓度。在自然界中，5α-CPS的原位浓度是鱼类释放和同时细菌降解的结果。为了解释这两个过程，我建议在不同的温度下确定不同大小和进食状态的个体鱼的5α-CPS释放速率。通过孵育加标已知浓度5α-CPS的湖水并随时间定量5α-CPS，确定不同温度下的细菌降解速率。除了DVM，生活史变化（LHC）是水蚤对鱼类的另一个非常重要的诱导防御。然而，LHC诱导利它素尚不清楚。在这里，我提出了最直接的测试方法，即5α-CPS是否会诱导LHC。如果没有，鱼孵育水的提取物将通过与高分辨率质谱仪耦合的HPLC在几轮增加的纯化中进行生物测定引导的纯化。将在成熟的LHC生物测定中检测HPLC产生的馏分。随后的非靶向代谢组学和片段化实验将旨在鉴定利它素。总体目标是（i）更准确地了解在准自然条件下5α-CPS在水蚤中的DVM诱导，并估计5α-CPS的产生和降解速率，以及（ii）鉴定LHC诱导的鱼类利它素。