Alberta Environment and Protected Areas, 4938 89th Street, Edmonton, AB T6E5K1 Canada; Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 Canada.
Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 Canada.
Aquat Toxicol. 2023 Aug;261:106636. doi: 10.1016/j.aquatox.2023.106636. Epub 2023 Jul 17.
For over a decade, intersex has been observed in rainbow darter (RD) (Etheostoma caeruleum) populations living downstream wastewater treatment plants (WWTPs) in the Grand River, Ontario, Canada. To further our understanding of intersex development in adult male fish, the current study addressed three objectives: i) can intersex be induced in adult male fish, ii) is there a specific window of exposure when adult male fish are more susceptible to developing intersex, and iii) can pre-exposed adult male fish recover from intersex? To assess intersex induction in adult male fish, wild male RD were exposed in the laboratory for 22 weeks (during periods of spawning, gonadal regression, and gonadal recrudescence) to environmentally relevant concentrations of 17α-ethinylestradiol (EE2) including nominal 0, 1, and 10 ng/L. Intersex rates and severity at 10 ng/L EE2 were similar to those observed historically in adult male populations living downstream WWTPs in the Grand River and confirmed previous predictions that 1-10 ng/L EE2 would cause these adverse effects. To assess a window of sensitivity in developing intersex, male RD were exposed to nominal 0, 1 or 10 ng/L EE2 for 4 weeks during three different periods of gonadal development, including (i) spawning, (ii) early recrudescence and (iii) late recrudescence. These short-term exposures revealed that intersex incidence and severity were greater when RD were exposed while gonads were fully developed (during spawning) compared to periods of recrudescence. To assess if RD recover from intersex, wild fish were collected downstream WWTPs in the Grand River and assessed for intersex both before and after a 22-week recovery period in clean water that included gonadal regression and recrudescence. Results showed that fish did not recover from intersex, with intersex rates and severity similar to those both before and after the transition to clean water. This study further advances our knowledge on intersex manifestation in adult male fish including their sensitivity to endocrine active compounds during different periods of their annual reproductive cycle and their limited ability to recover from intersex after onset of the condition.
十多年来，在加拿大安大略省格兰德河下游的废水处理厂（WWTP）中，人们观察到彩虹镖鱼（RD）（Etheostoma caeruleum）种群中存在雌雄间性现象。为了进一步了解成年雄性鱼类的雌雄间性发育，本研究旨在实现以下三个目标：i）能否在成年雄性鱼类中诱导出雌雄间性，ii）成年雄性鱼类在哪个特定的暴露窗口期更容易发生雌雄间性，以及 iii）预先暴露的成年雄性鱼类能否从雌雄间性中恢复。为了评估成年雄性鱼类的雌雄间性诱导，野生雄性 RD 在实验室中进行了 22 周的暴露实验（在繁殖期、性腺退化期和性腺复壮期），暴露于环境相关浓度的 17α-乙炔基雌二醇（EE2）中，包括名义上的 0、1 和 10ng/L。10ng/L EE2 诱导的雌雄间性发生率和严重程度与历史上在格兰德河下游 WWTP 中生活的成年雄性鱼类种群相似，证实了之前的预测，即 1-10ng/L EE2 会引起这些不利影响。为了评估雌雄间性发育的敏感窗口，雄性 RD 在三个不同的性腺发育时期（包括 i）繁殖期、ii）早期复壮期和 iii）晚期复壮期），分别暴露于名义上的 0、1 或 10ng/L EE2 中 4 周。这些短期暴露实验表明，当 RD 的性腺完全发育（在繁殖期）时，与复壮期相比，雌雄间性的发生率和严重程度更高。为了评估 RD 是否能从雌雄间性中恢复，在格兰德河下游的 WWTP 中收集了野生鱼类，并在为期 22 周的清洁水恢复期前后进行了雌雄间性评估，该恢复期包括性腺退化和复壮。结果表明，鱼类无法从雌雄间性中恢复，其雌雄间性发生率和严重程度与在清洁水过渡前后相似。本研究进一步提高了我们对成年雄性鱼类中雌雄间性表现的认识，包括它们在年度生殖周期不同时期对内分泌活性化合物的敏感性，以及它们在出现雌雄间性后从雌雄间性中恢复的能力有限。
