The University of Montana, Division of Biological Sciences, Flathead Lake Biological Station, 32125 Bio Station Lane, Polson, MT 59801, USA.
The University of Montana, 32 Campus Drive, Missoula, MT 59812, USA.
J Exp Biol. 2022 Sep 15;225(18). doi: 10.1242/jeb.244253. Epub 2022 Sep 20.
Like all taxa, populations of aquatic insects may respond to climate change by evolving new physiologies or behaviors, shifting their range, exhibiting physiological and behavioral plasticity, or going extinct. We evaluated the importance of plasticity by measuring changes in growth, survival and respiratory phenotypes of salmonfly nymphs (the stonefly Pteronarcys californica) in response to experimental combinations of dissolved oxygen and temperature. Overall, smaller individuals grew more rapidly during the 6-week experimental period, and oxygen and temperature interacted to affect growth in complex ways. Survival was lower for the warm treatment, although only four mortalities occurred (91.6% versus 100%). Nymphs acclimated to warmer temperatures did not have higher critical thermal maxima (CTmax), but those acclimated to hypoxia had CTmax values (in normoxia) that were higher by approximately 1°C. These results suggest possible adaptive plasticity of systems for taking up or delivering oxygen. We examined these possibilities by measuring the oxygen sensitivity of metabolic rates and the morphologies of tracheal gill tufts located ventrally on thoracic segments. Mass-specific metabolic rates of individuals acclimated to warmer temperatures were higher in acute hypoxia but lower in normoxia, regardless of their recent history of oxygen exposure during acclimation. The morphology of gill filaments, however, changed in ways that appeared to depress rates of oxygen delivery in functional hypoxia. Our combined results from multiple performance metrics indicate that rising temperatures and hypoxia may interact to magnify the risks to aquatic insects, but that physiological plasticity in respiratory phenotypes may offset some of these risks.
与所有分类群一样，水生昆虫种群可能会通过进化出新的生理机能或行为、改变其分布范围、表现出生理和行为可塑性，或者灭绝来应对气候变化。我们通过测量鲑鱼若虫（石蝇 Pteronarcys californica）在溶解氧和温度的实验组合下生长、存活和呼吸表型的变化，评估了可塑性的重要性。总的来说，在 6 周的实验期间，较小的个体生长得更快，而氧气和温度以复杂的方式相互作用影响生长。尽管只有 4 例死亡（91.6%对 100%），但高温处理的存活率较低。适应较高温度的若虫没有更高的临界热最大值（CTmax），但适应低氧的若虫在正常氧条件下的 CTmax 值高出约 1°C。这些结果表明，氧气摄取或输送系统可能具有适应性可塑性。我们通过测量代谢率的氧气敏感性和位于胸段腹侧的气管鳃簇的形态来检验这些可能性。适应较高温度的个体在急性缺氧下的比特定代谢率较高，但在正常氧下较低，而不管它们在适应期间最近的氧气暴露历史如何。然而，鳃丝的形态发生了变化，似乎降低了功能缺氧下的氧气输送速度。我们从多个性能指标得出的综合结果表明，气温升高和低氧可能会相互作用，增加水生昆虫的风险，但呼吸表型的生理可塑性可能会抵消其中的一些风险。
