Alluvial aquifers are key components of river floodplains and biodiversity worldwide, but they contain extreme environmental conditions and have limited sources of carbon for sustaining food webs. Despite this, they support abundant populations of aquifer stoneflies that have large proportions of their biomass carbon derived from methane. Methane is typically produced in freshwater ecosystems in anoxic conditions, while stoneflies (Order: Plecoptera) are thought to require highly oxygenated water. The potential importance of methane-derived food resources raises the possibility that stonefly consumers have evolved anoxia-resistant behaviors and physiologies. Here we tested the anoxic and hypoxic responses of 2445 stonefly individuals in three aquifer species and nine benthic species. We conducted experimental trials in which we reduced oxygen levels, documented locomotor activity, and measured survival rates. Compared to surface-dwelling benthic relatives, stoneflies from the alluvial aquifer on the Flathead River (Montana) performed better in hypoxic and anoxic conditions. Aquifer species sustained the ability to walk after 4-76 hours of anoxia versus one hour for benthic species, and survived on average 3× longer than their benthic counterparts. Aquifer stoneflies also sustained aerobic respiration down to much lower levels of ambient oxygen. We show that aquifer taxa have gene sequences for hemocyanin, an oxygen transport respiratory protein, representing a possible mechanism for surviving low oxygen. This remarkable ability to perform well in low-oxygen conditions is unique within the entire order of stoneflies (Plecoptera) and uncommon in other freshwater invertebrates. These results show that aquifer stoneflies can exploit rich carbon resources available in anoxic zones, which may explain their extraordinarily high abundance in gravel-bed floodplain aquifers. These stoneflies are part of a novel food web contributing biodiversity to river floodplains.

中文翻译：

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来自漫滩含水层的石蝇具有显着的缺氧耐受性

冲积含水层是全球河流泛滥平原和生物多样性的关键组成部分，但它们包含极端的环境条件，并且用于维持食物网的碳来源有限。尽管如此，它们仍然支持大量的含水层石蝇种群，这些石蝇的大部分生物量碳来自甲烷。甲烷通常在缺氧条件下在淡水生态系统中产生，而石蝇（目：Plecoptera）被认为需要高度含氧的水。甲烷衍生食物资源的潜在重要性增加了石蝇消费者进化出抗缺氧行为和生理的可能性。在这里，我们测试了 3 个含水层物种和 9 个底栖物种中 2445 只石蝇个体的缺氧和缺氧反应。我们进行了实验性试验，在这些试验中我们降低了氧气水平、记录了运动活动并测量了存活率。与地表栖息的底栖近缘种相比，来自弗拉特黑德河（蒙大拿州）冲积含水层的石蝇在缺氧和缺氧条件下表现更好。含水层物种在缺氧 4-76 小时后保持行走能力，而底栖物种则为 1 小时，并且平均存活时间比底栖物种长 3 倍。含水层石蝇也将有氧呼吸维持在低得多的环境氧气水平。我们表明含水层分类群具有血蓝蛋白的基因序列，血蓝蛋白是一种氧运输呼吸蛋白，代表了在低氧条件下生存的可能机制。这种在低氧条件下表现良好的非凡能力在整个石蝇目（鳞翅目）中是独一无二的，在其他淡水无脊椎动物中并不常见。这些结果表明，含水层石蝇可以利用缺氧区中丰富的碳资源，这可以解释它们在砾石床漫滩含水层中的异常高丰度。这些石蝇是为河流泛滥平原贡献生物多样性的新型食物网的一部分。