Data_Sheet_1_One Kairomone and Multiple Effects in Daphnia Species—5α-Cyprinol Sulfate Induces Morphological Defenses in the Invasive Species Daphnia lumholtzi.docx

Recently, the first chemical cues, which induce defenses in freshwater zooplankton of the genus Daphnia have been identified. Still it is unknown how general these so-called kairomones are and if they are perceived by and thereby benefitting invasive species. We here report the chemical identity of the fish-derived chemical signal that induces morphological defensive structures in the invasive species Daphnia lumholtzi. We used bioassay-guided isolation (LC-MS) of incubation water of fish and identified the bile salt 5α-cyprinol sulfate (5α-CPS) as the kairomone. We confirmed this finding by bioassays, in which D. lumholtzi was exposed to purified 5α-CPS sulfate from fish bile and showed that 10 pM 5α-CPS induces significantly elongated helmets and spines in relation to body length. These results identify on one hand another Daphnia species besides Daphnia magna, which is responding to this particular fish-borne kairomone, and on the other hand they reveal another defense that the kairomone induces besides diel vertical migration (DVM). Taken together a high evolutionary conservancy of the molecular mechanism behind inducible defenses in Daphnia spp. against fish can be deduced. It is reasonable to expect that 5α-CPS is involved in further predator—prey communication between Daphnia and fish, which may be of special ecological relevance with regard to invasive species as D. lumholtzi.

近日，首个可诱导水蚤属（Daphnia）淡水浮游动物产生防御反应的化学信号被成功鉴定。但目前仍不清楚这类被称为利它素（kairomone）的信号分子的普适性，以及它们是否能被入侵物种识别并使其获益。本研究报道了一种源自鱼类的化学信号的化学本质，该信号可诱导入侵物种Daphnia lumholtzi产生形态学防御结构。本研究通过对鱼类养殖水体进行生物活性导向分离（液相色谱-质谱联用，LC-MS），鉴定出胆汁盐5α-鲤醇硫酸酯（5α-cyprinol sulfate, 5α-CPS）为该利它素。本研究通过生物测定实验验证了这一结论：将D. lumholtzi暴露于从鱼类胆汁中纯化得到的5α-CPS中，发现10皮摩尔每升的5α-CPS可使其头盔和棘刺相对于体长显著伸长。本研究结果一方面证实了除大型溞（Daphnia magna）外，另有一类水蚤属物种可响应这种鱼类来源的利它素；另一方面则揭示了该利它素除诱导昼夜垂直迁移（diel vertical migration, DVM）外，还可诱发另一种防御反应。综合来看，可推断出水蚤属（Daphnia）物种针对鱼类的诱导型防御反应背后的分子机制具有高度的进化保守性。据此可合理推测，5α-CPS可能参与水蚤与鱼类之间更多的捕食者-猎物间信息交流，这对于D. lumholtzi这类入侵物种而言，可能具有特殊的生态学意义。