Schmidt Matthias, Windisch Heidrun Sigrid, Ludwichowski Kai-Uwe, Seegert Sean Lando Levin, Pörtner Hans-Otto, Storch Daniela, Bock Christian
Alfred-Wegener-Institute Helmholtz-Centre for Polar- and Marine Research, Section Integrative Ecophysiology, Am Handelshafen 12, 27570 Bremerhaven, Germany.
Department of Biology/Chemistry, University of Bremen, PO 330440, 28334 Bremen, Germany.
Front Zool. 2017 Oct 30;14:49. doi: 10.1186/s12983-017-0238-5. eCollection 2017.
Exposure to future ocean acidification scenarios may alter the behaviour of marine teleosts through interference with neuroreceptor functioning. So far, most studies investigated effects of ocean acidification on the behaviour of fish, either isolated or in combination with environmental temperature. However, only few physiological studies on this issue were conducted despite the putative neurophysiological origin of the CO-induced behavioural changes. Here, we present the metabolic consequences of long-term exposure to projected ocean acidification (396-548 μatm CO under control and 915-1272 μatm under treatment conditions) and parallel warming in the brain of two related fish species, polar cod (, exposed to 0 °C, 3 °C, 6 °C and 8 °C) and Atlantic cod (, exposed to 3 °C, 8 °C, 12 °C and 16 °C). It has been shown that is behaviourally vulnerable to future ocean acidification scenarios, while demonstrates behavioural resilience.
We found that temperature alters brain osmolyte, amino acid, choline and neurotransmitter concentrations in both species indicating thermal responses particularly in osmoregulation and membrane structure. In changes in amino acid and osmolyte metabolism at the highest temperature tested were also affected by CO, possibly emphasizing energetic limitations. We did not observe changes in neurotransmitters, energy metabolites, membrane components or osmolytes that might serve as a compensatory mechanism against CO induced behavioural impairments. In contrast to , such temperature limitation was not detected in ; however, at 8 °C, CO induced an increase in the levels of metabolites of the glutamate/GABA-glutamine cycle potentially indicating greater GABAergic activity in . Further, increased availability of energy-rich substrates was detected under these conditions.
Our results indicate a change of GABAergic metabolism in the nervous system of close to the optimum of the temperature range. Since a former study showed that juvenile might be slightly more behaviourally resilient to CO at this respective temperature, we conclude that the observed change of GABAergic metabolism could be involved in counteracting OA induced behavioural changes. This may serve as a fitness advantage of this respective species compared to in a future warmer, more acidified polar ocean.
暴露于未来海洋酸化情景下可能会通过干扰神经受体功能改变硬骨鱼类的行为。到目前为止，大多数研究调查了海洋酸化对鱼类行为的影响，这些研究要么单独进行，要么与环境温度相结合。然而，尽管二氧化碳诱导的行为变化可能源于神经生理学，但关于这个问题的生理学研究却很少。在此，我们展示了长期暴露于预计的海洋酸化环境（对照条件下为396 - 548微大气压二氧化碳，处理条件下为915 - 1272微大气压）以及两种相关鱼类——极地鳕鱼（暴露于0°C、3°C、6°C和8°C）和大西洋鳕鱼（暴露于3°C、8°C、12°C和16°C）大脑中同时变暖的代谢后果。已有研究表明，极地鳕鱼在行为上易受未来海洋酸化情景的影响，而大西洋鳕鱼则表现出行为弹性。
我们发现温度会改变这两种鱼类大脑中的渗透质、氨基酸、胆碱和神经递质浓度，表明存在热响应，特别是在渗透调节和膜结构方面。在极地鳕鱼中，测试的最高温度下氨基酸和渗透质代谢的变化也受到二氧化碳的影响，这可能突出了能量限制。我们没有观察到神经递质、能量代谢物、膜成分或渗透质的变化，这些变化可能作为针对二氧化碳诱导的行为损伤的补偿机制。与极地鳕鱼不同，在大西洋鳕鱼中未检测到这种温度限制；然而，在8°C时，二氧化碳会导致谷氨酸/γ-氨基丁酸-谷氨酰胺循环代谢物水平升高，这可能表明大西洋鳕鱼中γ-氨基丁酸能活性更高。此外，在这些条件下检测到富含能量的底物可用性增加。
我们的结果表明，在接近温度范围最佳值时，大西洋鳕鱼神经系统中的γ-氨基丁酸能代谢发生了变化。由于之前的一项研究表明，在这个特定温度下，幼年大西洋鳕鱼对二氧化碳的行为弹性可能略高，我们得出结论，观察到的γ-氨基丁酸能代谢变化可能参与抵消海洋酸化诱导的行为变化。与极地鳕鱼相比，并在未来更温暖、酸化程度更高的极地海洋环境中，这可能是该特定物种的一个适应性优势。
