Action of two endocrine disrupters on the sexual differenciation of Nile tilapia

ABSTRACT Endocrine disruptors are exogenous substances that can impair one or more functions of the endocrine system and cause adverse effects to the health of an intact organism. The main goal of this study was to evaluate the effect of the endocrine disruptors 17β-estradiol (E2) and 17α-ethinyl estradiol (EE2) on the sexual differentiation of Nile tilapia during spawning. Six treatments and one control with three replications, totalizing 21 experimental units, were assessed in a completely randomized design. Hormones were dosed at concentrations of 250, 500, and 1,000 ng L−1 (treatments E2-250, E2-500, E2-1,000, EE2-250, EE2-500, and EE2-1,000). Exposure to hormones occurred during the first 28 days of life. After this period, water was completely renewed and individuals kept in their respective experimental units for another 60 days, totaling 88 days. At the end of this period, animals were euthanized by ice desensitization for gonad extraction, slide preparation, and observation under an optical microscope. At the end of the experiment, the results indicated that the type of hormone and hormone concentration differentially affected the parameters of zootechnical performance. A significant difference (p<0.05) was observed in the condition factor between control and treatments. Intersex individuals were observed in treatments of both hormones, except for the control treatment. In addition, malformations were observed in individuals submitted to treatments, mainly in the head region. Thus, the presence of the chemical compounds 17β-estradiol and 17α-ethinylestradiol severely affected the development and sexual differentiation of Nile tilapia.

摘要：内分泌干扰物（Endocrine disruptors）是一类可损伤内分泌系统一项或多项功能，并对完整生物体健康产生不利影响的外源性物质。本研究旨在评估内分泌干扰物17β-雌二醇（17β-estradiol，E2）与17α-乙炔雌二醇（17α-ethinyl estradiol，EE2）在产卵期对尼罗罗非鱼（Nile tilapia）性别分化的影响。实验采用完全随机设计，设置6个处理组与1个对照组，每组设置3次生物学重复，总计21个实验单元。激素暴露浓度分别设置为250、500与1000 ng·L⁻¹，对应处理组依次为E2-250、E2-500、E2-1000、EE2-250、EE2-500及EE2-1000。激素暴露周期为幼鱼出生后的前28天。暴露期结束后，完全更换养殖用水，将实验鱼保留于原实验单元中继续饲养60天，总实验周期共计88天。实验周期结束后，采用冰麻法处死实验鱼，摘取性腺制备组织切片，随后在光学显微镜下进行观察。结果表明，激素种类与激素浓度对水产养殖性能参数存在差异化影响。对照组与各处理组的鱼体条件指数存在显著差异（p<0.05）。除对照组外，两种激素的各处理组中均观察到间性个体。此外，各处理组的实验鱼均出现畸形症状，且主要集中于头部区域。综上，17β-雌二醇与17α-乙炔雌二醇这两种化学物质会严重干扰尼罗罗非鱼的生长发育与性别分化过程。