Qiu Xuchun, Nomichi Sayaka, Chen Kun, Honda Masato, Kang Ik Joon, Shimasaki Yohei, Oshima Yuji
Laboratory of Marine Environmental Science, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
International Student Center, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
Aquat Toxicol. 2017 Nov;192:148-154. doi: 10.1016/j.aquatox.2017.09.012. Epub 2017 Sep 14.
Although most exposures to chlorpyrifos (CPF) in natural flowing waters are brief and episodic, there have been a few reports of the persistence of abnormal fish behaviors caused by such acute exposure. The present study focused on the behavioral and biochemical responses of Japanese medaka (Oryzias latipes) to acute, sublethal exposure to CPF, as well as the persistence of the effects during a 3-week recovery test in CPF-free water. The medaka became hyperactive and exhibited an elevated anxiety state after a 4-day exposure to 0.024mg/L of CPF, but they recovered from these abnormal behavioral responses within 7days of recovery treatment. In contrast, persistent impacts on some startle responses to a sudden stimulation (induced by a ball drop) were observed in medaka exposed to CPF. The reaction latency did not change immediately after the 4-day exposure, but was significantly prolonged by as much as 21days after the termination of exposure. The post-stimulus swimming distance within 5s significantly decreased on the day immediately after the 4-day exposure, but it significantly increased after 7days of recovery treatment. The activity of acetylcholinesterase (AChE) in the brains of medaka was significantly inhibited on the day immediately after the 4-day exposure, but it returned to 80% and 110% of that in control fish on days 7 and 21 of the recovery period, respectively. However, AChE activities in the eyes of exposed medaka were persistently inhibited and declined to 33%, 71%, and 72% of that in control fish on days 0 (immediately after the 4-day exposure), 7, and 21 of recovery, respectively. Correlation analysis suggested that the changes of AChE activities in the brains of medaka may underlie some of the observed acute behavioral changes, and the changes of AChE activities in the eyes may contribute to the persistence of the abnormalities in the reaction latency of the startle response. Our findings suggest that medaka need a long time to recover from acute, sublethal exposure to CPF, and the persistence of the behavioral abnormalities might affect their fitness in natural habitats.
尽管在天然流动水体中大多数毒死蜱（CPF）暴露是短暂且偶发的，但已有一些报告称这种急性暴露会导致鱼类异常行为持续存在。本研究聚焦于日本青鳉（Oryzias latipes）对急性、亚致死剂量CPF暴露的行为和生化反应，以及在无CPF水中进行的3周恢复试验期间这些影响的持续性。青鳉在暴露于0.024mg/L的CPF 4天后变得多动，并表现出焦虑状态升高，但在恢复处理7天内从这些异常行为反应中恢复。相比之下，在暴露于CPF的青鳉中观察到对突然刺激（由落球诱导）的一些惊吓反应存在持续性影响。反应潜伏期在4天暴露后没有立即改变，但在暴露终止后长达21天显著延长。4天暴露后紧接着的当天，5秒内刺激后的游泳距离显著缩短，但在恢复处理7天后显著增加。青鳉脑中乙酰胆碱酯酶（AChE）的活性在4天暴露后紧接着的当天显著受到抑制，但在恢复期的第7天和第21天分别恢复到对照鱼的80%和110%。然而，暴露青鳉眼中的AChE活性持续受到抑制，在恢复的第0天（4天暴露后紧接着）、第7天和第21天分别降至对照鱼的33%、71%和72%。相关性分析表明，青鳉脑中AChE活性的变化可能是一些观察到的急性行为变化的基础，而眼中AChE活性的变化可能导致惊吓反应反应潜伏期异常的持续存在。我们的研究结果表明，青鳉从急性、亚致死剂量CPF暴露中恢复需要很长时间，行为异常的持续存在可能会影响它们在自然栖息地中的适应性。
