Data from: 5α-cyprinol sulfate, a bile salt from fish, induces diel vertical migration in Daphnia

Prey are under selection to minimize predation losses. In aquatic environments many prey use chemical cues released by predators, which initiate predator-avoidance. A prominent example of behavioural predator-avoidance constitutes diel vertical migration (DVM) in the freshwater microcrustacean Daphnia spp., which is induced by chemical cues (kairomones) released by planktivorous fish. In a bioassay-guided approach using liquid chromatography and mass spectrometry we isolated the kairomone from fish incubation water and identified it as 5α-cyprinol sulfate inducing DVM in Daphnia at picomolar concentrations. The role of 5α-cyprinol sulfate in lipid digestion in fish explains why from an evolutionary perspective fish has not stopped releasing 5α-cyprinol sulfate despite the disadvantages for the releaser. The identification of the DVM-inducing kairomone enables investigating its spatial and temporal distribution and the underlying molecular mechanism of its perception. Furthermore, it allows to test if fish-mediated inducible defenses in other aquatic invertebrates are triggered by the same compound.

猎物会受到自然选择的作用，以最大限度降低被捕食的损失。在水生环境中，多数猎物会利用捕食者释放的化学信号，以此启动反捕食行为。一类典型的行为性反捕食策略是淡水微型甲壳动物水蚤属（Daphnia spp.）的昼夜垂直迁移（Diel Vertical Migration, DVM），该行为由浮游植食性鱼类释放的利它素（kairomones）诱导产生。本研究通过生物测定导向的液相色谱-质谱联用法，从鱼类养殖水体中分离得到该利它素，并鉴定其为5α-硫酸胆甾烷醇（5α-cyprinol sulfate）——该物质可在皮摩尔浓度下诱导水蚤产生昼夜垂直迁移行为。5α-硫酸胆甾烷醇在鱼类脂质消化过程中所起到的作用，从进化视角解释了为何尽管释放该物质会对释放者自身产生不利影响，鱼类仍未停止分泌该化合物。此次昼夜垂直迁移诱导型利它素的成功鉴定，不仅为研究其时空分布以及感知该物质的潜在分子机制提供了可能，还可用于验证其他水生无脊椎动物中由鱼类介导的诱导型防御是否均由同一化合物触发。