Ongoing pollution of aquatic ecosystems with neurochemical compounds warrants an improved understanding of how this affects key organisms. Neurochemicals are shown to alter the behaviour of common study species but it remains difficult to translate these results to biologically meaningful predictions across taxa. This is partly because studies on species with non-generic life-history strategies such as many freshwater crustaceans are currently underrepresented. Here, we use a laboratory experiment to assess baseline behavioural variation (spontaneous activity level and geotaxic behaviour) in the freshwater fairy shrimp Branchipodopsis wolfi and how this is affected by chronic exposure to an environmentally-relevant concentration of the anxiolytic pharmaceutical fluoxetine. The more conspicuously coloured and larger females of the species were overall less active and more benthic than males. Moreover, amongst females, vertical activity was negatively associated with size, while an opposite relationship was found for males. These trade-offs are likely part of an antipredator strategy to reduce the probability of being detected by visual hunters, but disappeared after exposure to fluoxetine. This is of particular interest since it is an effective proof of principle that neurochemicals may impact ecologically-relevant trade-offs between conspicuous morphology and antipredator behaviour. In natural ecosystems, such disturbed antipredator behavioural responses could have far-reaching fitness consequences.

神经化学化合物对水生生态系统的持续污染需要更好地了解这如何影响关键生物。神经化学物质被证明会改变常见研究物种的行为，但仍难以将这些结果转化为对整个分类群具有生物学意义的预测。这部分是因为对具有非通用生活史策略的物种（例如许多淡水甲壳类动物）的研究目前代表性不足。在这里，我们使用实验室实验来评估淡水仙女虾Branchipodopsis wolfi 的基线行为变化（自发活动水平和地理定位行为）以及长期暴露于环境相关浓度的抗焦虑药物氟西汀对其有何影响。与雄性相比，该物种中颜色更显眼、体型更大的雌性总体上较不活跃且底栖性更强。此外，在女性中，垂直活动与体型呈负相关，而男性则呈相反的关系。这些权衡可能是减少被视觉猎人发现的可能性的反捕食者策略的一部分，但在暴露于氟西汀后就消失了。这是特别令人感兴趣的，因为它有效地证明了神经化学物质可能会影响显着形态和反捕食者行为之间的生态相关权衡。在自然生态系统中，