Pollution from regularly used substances such as pharmaceuticals, cleaning agents, and even food and beverages is an increasing problem in the environment. Caffeine, a commonly ingested stimulant, is one such contaminant that has been detected in aquatic environments worldwide. Yet, little is known about how ecologically relevant concentrations of caffeine influence the morphology, behaviour, and physiology of exposed organisms. To address this knowledge gap, we exposed fathead minnow () to three caffeine treatments: a freshwater control (nominal: 0 ng/L), a low (nominal: 1,000 ng/L) and high environmentally relevant dose (nominal: 10,000 ng/L), for 35 days. We tested the learning abilities, anxiety, metabolic rates, and morphological features of exposed vs. control fish. Caffeine exposure did not affect the ability of fish to learn but did influence anxiety levels. Over the course of repeated anxiety testing, unexposed control fish visited a black square more often while fish exposed to low levels of caffeine did not, potentially indicating that these fish remained in a more anxious state. While caffeine did not impact metabolism, fish growth, or body size, it was associated with lower liver investment—although this response was only observed in our low caffeine treatment. Overall, our results suggest that even relatively low concentrations of caffeine may impact the liver size and anxiety of exposed fish, but further research is needed to assess how extended exposure to caffeine impacts fitness. Given the increase in anthropogenic contaminants in aquatic environments, it is important that we continue to investigate their effects on the organisms exposed to them.

中文翻译：

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咖啡因对黑头呆鱼行为和生理的影响


药品、清洁剂、甚至食品和饮料等常用物质造成的污染已成为环境中日益严重的问题。咖啡因是一种常见的摄入兴奋剂，也是在全世界水生环境中检测到的污染物之一。然而，人们对咖啡因的生态相关浓度如何影响暴露的生物体的形态、行为和生理机能知之甚少。为了弥补这一知识差距，我们将黑头呆鱼暴露于三种咖啡因处理中：淡水对照（标称：0 ng/L）、低剂量（标称：1,000 ng/L）和高环境相关剂量（标称：10,000 ng/L）。 L），持续 35 天。我们测试了暴露鱼与对照鱼的学习能力、焦虑、代谢率和形态特征。接触咖啡因不会影响鱼的学习能力，但会影响焦虑水平。在重复的焦虑测试过程中，未暴露的对照鱼更频繁地访问黑色方块，而暴露于低水平咖啡因的鱼却没有，这可能表明这些鱼仍处于更焦虑的状态。虽然咖啡因不会影响新陈代谢、鱼类生长或体型，但它与较低的肝脏投资有关——尽管这种反应仅在我们的低咖啡因治疗中观察到。总体而言，我们的结果表明，即使咖啡因浓度相对较低，也可能会影响鱼类的肝脏大小和焦虑程度，但需要进一步研究来评估长期接触咖啡因如何影响健康。鉴于水生环境中人为污染物的增加，我们继续研究它们对接触它们的生物体的影响非常重要。