The recent discovery of illicit drugs in the aquatic environment has raised concerns about the possible effects on the aquatic fauna, because of the pharmacological activity of these substances. Cocaine is an illicit drug widespread in surface waters since it is the third most widely used drug in North America, Western and Central Europe, and the second in Latin America and the Caribbean. The aim of this study was to evaluate the influence of environmental concentrations of cocaine on the gills of the European eel (Anguilla anguilla). The gills of male silver eels exposed to 20 ng L⁻¹ of cocaine for fifty days were compared to control, vehicle control and post-exposure recovery ten days groups. The following parameters were evaluated: the thickness of the interlamellar epithelium (TIE), the length of the secondary lamellae (LSL) and the fraction of the interlamellar epithelium and the secondary lamellae occupied by the mucous cells (MC(IE-SL)FA) 3) the plasma cortisol and prolactin levels. After cocaine exposure, the gill epithelium appeared hyperplastic. The following changes were observed: proliferation in the interlamellar epithelium; partial and total fusion of the secondary lamellae, that appeared shortened and dilated; epithelial lifting and aneurism in the secondary lamellae. Moreover, in cocaine exposed eels, an increase in TIE and MC(IE-SL)FA and a decrease in LSL were observed. These changes were still present ten days after the interruption of cocaine exposure. Plasma levels of both cortisol and prolactin increased after cocaine exposure; ten days after the interruption of cocaine exposure, the plasma cortisol levels were still higher, whereas the plasma prolactin levels were lower, than control values. Our results show that even a chronic exposure to low environmental cocaine concentrations severely harms the eel gills, suggesting damages to their functions, and potentially affecting the survival of this species.

由于这些物质的药理活性，最近在水生环境中发现非法药物引起了人们对水生动物可能产生影响的担忧。可卡因是一种非法药物，广泛存在于地表水域，因为它是北美，西欧和中欧地区第三大最广泛使用的药物，而在拉丁美洲和加勒比地区则是第二大使用最广泛的药物。这项研究的目的是评估可卡因的环境浓度对欧洲鳗（（Anguilla anguilla）g的影响。暴露于20 ng L ^-1的雄性银e的将50天的可卡因与对照组，赋形剂对照和暴露后恢复十天组进行比较。评估了以下参数：层间上皮的厚度（TIE），次级层的长度（LSL）以及粘膜细胞所占的层间上皮和次级层的比例（MC（IE-SL）FA） 3）血浆皮质醇和催乳素水平。可卡因暴露后，the上皮出现增生。观察到以下变化：层间上皮中的增殖；次生薄片的部分和全部融合，似乎缩短并扩张；继发性上皮中的上皮提升和动脉瘤。此外，在可卡因暴露的鳗鱼中，观察到TIE和MC（IE-SL）FA升高，而LSL降低。可卡因暴露中断十天后，这些变化仍然存在。可卡因暴露后血浆皮质醇和催乳激素水平增加；可卡因暴露中断后十天，血浆皮质醇水平仍然较高，而血浆催乳素水平则低于对照值。我们的结果表明，即使长期暴露于低环境可卡因浓度也会严重危害鳗g，表明它们的功能受到损害，并可能影响该物种的生存。