Freshwater zooplankton Daphnia magna has been widely used in ecotoxicology studies. During the last 20 years, it has been demonstrated that the topical application of juvenile hormone (JH) or JH analogs to mother daphnids induce male offspring production. Based on this finding, an in vivo screening validation method for chemicals with JH agonistic effect has developed. Although this screening system successfully identified a number of JH‐like chemicals, molecular mechanisms underlying the male sex‐determining process remain largely unknown. To address this issue, we established a reliable male‐ or female‐producing system using Daphnia pulex WTN6 strain by changing the rearing photoperiod. Taking advantage of this rearing system, we successfully found several factors involving male sex determination such as ionotropic glutamate receptors, protein kinase C and pantothenate. Here, we used two D. magna strains that can also control the production of female or male offspring by photoperiod differences as model species for ecotoxicology studies. We demonstrated that either treatment of antagonist of ionotropic glutamate receptors or inhibitor of protein kinase C strongly suppressed male offspring production even under male‐producing conditions. Moreover, we revealed that male sex‐determining processes are likely diverged between D. magna and D. pulex based on the current experiment. This study provides a fine experimental method for in vivo screening not only JH agonists but also JH antagonists. Moreover, using daphnids with photoperiod‐dependent sex determination manner will hugely contribute to understanding the mode‐of‐action of JH in daphnids.

中文翻译：

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淡水甲壳类大型水蚤中光周期依赖性性别决定的法尼酸甲酯调控机制。

淡水浮游动物Daphnia magna已广泛用于生态毒理学研究。在过去的 20 年里，已经证明保幼激素 (JH) 或 JH 类似物对母水蚤的局部应用会诱导雄性后代的产生。基于这一发现，开发了一种具有 JH 激动作用的化学品的体内筛选验证方法。尽管该筛选系统成功识别了许多 JH 样化学物质，但男性性别决定过程的分子机制在很大程度上仍然未知。为了解决这个问题，我们使用Daphnia pulex建立了一个可靠的雄性或雌性生产系统WTN6 通过改变饲养光周期产生菌株。利用这种饲养系统，我们成功地发现了几个涉及雄性性别决定的因素，如离子型谷氨酸受体、蛋白激酶 C 和泛酸。在这里，我们使用了两个D. magna菌株，它们也可以通过光周期差异控制雌性或雄性后代的产生，作为生态毒理学研究的模型物种。我们证明，即使在雄性产生条件下，离子型谷氨酸受体拮抗剂或蛋白激酶 C 抑制剂的治疗也能强烈抑制雄性后代的产生。此外，我们发现雄性决定过程可能在D. magna和D. pulex之间存在分歧根据目前的实验。该研究为体内筛选JH激动剂和JH拮抗剂提供了一种很好的实验方法。此外，使用具有光周期依赖性性别决定方式的水蚤将极大地有助于了解水蚤中 JH 的作用方式。