The increased presence of emergent compounds, such as pharmaceuticals drugs, in the aquatic compartment has been acknowledged as an evolving environmental issue whose consequences are not yet fully characterized. Specific classes of pharmaceutical drugs, such as fluoroquinolone antibiotics, can exert toxic effects to non-target species with ecological significance, since these compounds are environmentally stable and persistent, and may interact with some of the key physiologic processes of organisms. Despite such characteristics, knowledge about the effects of these drugs is still scarce, especially to non-target organisms. The present study aimed to evaluate the effects of chronic and acute exposures of the cladoceran Daphnia magna to the fluoroquinolone antibiotic ciprofloxacin. Putative toxic effects were assessed, following acute and chronic exposures to ecologically relevant concentrations of ciprofloxacin, through enzymatic (cholinesterase – ChEs, catalase – CAT, glutathione S-transferases – GSTs) and non-enzymatic (thiobarbituric acid reactive substances – TBARS, glycogen – Gly) biomarkers. In addition, we also determined behavioural (swimming distance – SD) and morphological (body length of the first brood – BL1B) endpoints in animals exposed to this drug. Ciprofloxacin acute exposure resulted in increased CAT and ChEs activities, and inhibited GSTs activity. After chronic exposure, ChEs activity was significantly inhibited, while GSTs activity was significantly enhanced. TBARS levels were only increased at higher concentrations of ciprofloxacin. CAT activity and Gly content did not evidence a clear and significant pattern of variation. SD was slightly inhibited during dark cycles. BL1B presented a significant decrease for animals subjected to an intermediate concentration. Results showed that even ecologically relevant concentrations of ciprofloxacin may cause oxidative stress in individuals of D. magna. The present study showed important data that corroborate the occurrence of significant biochemical alterations in key features of an aquatic organism when exposed to relevant levels of a widely used antibiotic, establishing essential links between environmental exposure to this specific drug and putative toxic challenges that may result in irreversible changes and damages, especially at the individual level. However, changes in the size of neonates suggest that population alterations are likely to occur under real scenarios of chronic contamination by this drug.

水生区室中涌现的化合物（例如药品）的存在增加已被认为是一个不断演变的环境问题，其后果尚未得到充分表征。特定种类的药物，例如氟喹诺酮抗生素，会对具有生态学意义的非目标物种产生毒性作用，因为这些化合物在环境上稳定且持久，并且可能与生物体的某些关键生理过程相互作用。尽管具有这些特征，但是对于这些药物的作用的知识仍然很少，特别是对于非靶标生物而言。本研究旨在评估锁骨水蚤Daphnia magna的慢性和急性暴露的影响。氟喹诺酮类抗生素环丙沙星。在急性和慢性暴露于生态相关浓度的环丙沙星之后，通过酶促（胆碱酯酶– ChEs，过氧化氢酶– CAT，谷胱甘肽S-转移酶– GSTs）和非酶促（硫代巴比妥酸反应性物质– TBARS，糖原– Gly）生物标志物。此外，我们还确定了接触该药物的动物的行为（游动距离– SD）和形态学（第一个雏鸡的体长– BL1B）终点。环丙沙星急性暴露导致CAT和ChEs活性增加，并抑制了GSTs活性。慢性暴露后，ChEs活性被显着抑制，而GSTs活性则显着增强。仅当环丙沙星浓度较高时，TBARS水平才会增加。CAT活性和Gly含量并未显示出清晰明显的变异模式。在黑暗周期中，SD受到轻微抑制。对于中等浓度的动物，BL1B显着降低。结果表明，即使在生态上相关的环丙沙星浓度也可能导致个体的氧化应激。D.玛格纳（D. magna）。本研究表明，重要的数据证实了当暴露于广泛使用的抗生素的相关水平时，水生生物关键特征发生重大生化变化的现象，这在环境中对该特定药物的暴露与可能导致不可逆转的变化和损害，尤其是在个人层面上。但是，新生儿大小的变化表明，在这种药物造成慢性污染的真实情况下，人群的改变很可能发生。