Université de Pau et des Pays de l'Adour, E2S UPPA, INRAE, ECOBIOP, Aquapôle INRAE, MIRA, F64310, Saint-Pée-sur-Nivelle, France; INRAE, Université de Pau et des Pays de l'Adour, E2S UPPA, NuMéA, F64310, Saint-Pée-sur-Nivelle, France.
Université de Pau et des Pays de l'Adour, E2S UPPA, INRAE, ECOBIOP, Aquapôle INRAE, MIRA, F64310, Saint-Pée-sur-Nivelle, France.
Chemosphere. 2020 Sep;255:127020. doi: 10.1016/j.chemosphere.2020.127020. Epub 2020 May 10.
The effect of methylmercury (MeHg) was investigated in glass eel migration behavior and metabolism. To migrate up estuary, glass eels synchronize their swimming activity to the flood tide and remain on or in the substratum during ebb tide. Following seven days of exposure to MeHg (100 ng L), glass eels migration behavior was expressed by their swimming synchronization to the water current reversal every 6.2 h (mimicking the alternation of flood and ebb tides) and their swimming activity level. In relation to their behavior, we then analyzed the energy-related gene expression levels in individual head, viscera and muscle. Results showed that MeHg decreased the number of glass eels synchronized to the change in water current direction and their swimming activity level. This last effect was more pronounced in non-synchronized fish than in synchronized ones, supporting the idea that non-synchronized glass eels could be more vulnerable to stress. As regard the expression of energy-related genes, no significant difference was observed between control and MeHg-exposed fish. In contrast, when the swimming activity levels were plotted against transcriptional responses, positive correlations were evidenced in viscera and especially in the head of exposed glass eels but not in control. Finally, it is noteworthy that non-synchronized glass eels displayed lower expression level of metabolism genes than their synchronized counterpart, but only in the head. Altogether, these results support the interest of focusing on the head to investigate the facultative migration behavior in glass eels and the effect of environmental stressors on this rhythmic behavior.
本研究旨在探讨甲基汞（MeHg）对玻璃鳗洄游行为和代谢的影响。为了溯河洄游至河口，玻璃鳗会同步其游泳活动，以适应涨潮，并在退潮时停留在或隐藏在底质中。在暴露于 MeHg（100ng/L）七天后，玻璃鳗通过其对每 6.2 小时一次的水流反转的游泳同步性（模拟涨潮和退潮的交替）及其游泳活动水平来表达其洄游行为。与它们的行为相关，我们随后分析了个体头部、内脏和肌肉中与能量相关的基因表达水平。结果表明，MeHg 降低了同步改变水流方向的玻璃鳗的数量及其游泳活动水平。这种最后一种效应在非同步鱼类中比在同步鱼类中更为明显，这支持了非同步玻璃鳗可能更容易受到压力的观点。至于与能量相关的基因表达，对照组和 MeHg 暴露组之间没有观察到显著差异。相比之下，当将游泳活动水平与转录反应进行比较时，暴露的玻璃鳗的内脏中表现出明显的正相关，尤其是头部，而对照组则没有。最后，值得注意的是，非同步玻璃鳗的代谢基因表达水平低于同步玻璃鳗，但仅在头部。总之，这些结果支持了将重点放在头部来研究玻璃鳗的适应性洄游行为以及环境胁迫对这种节律行为的影响的研究。
