Hyperoxia Does Not Extend Critical Thermal Maxima (CTmax) in White- or Red-Blooded Antarctic Notothenioid Fishes
Hyperoxia Does Not Extend Critical Thermal Maxima (CTmax) in White- or Red-Blooded Antarctic Notothenioid Fishes
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DOI：
10.1086/684812
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发表时间：
2016-01-01
影响因子：
1.6
通讯作者：
Crockett, Elizabeth L.
中科院分区：
文献类型：
--
作者：
Devor, Devin P.;Kuhn, Donald E.;Crockett, Elizabeth L.
了解是什么限制了生物体耐受温度升高的能力是比较生物学的一个关键目标。使用南极notothenioid鱼类的实验系统，我们试图确定是否是氧需求和氧供应之间的不匹配负责设置热耐受性限制。以往的研究表明，缺乏血红蛋白的南极冰鱼（科），有较低的临界温度最大值（CTmax）比从同一地区的南极（西南极半岛）收集的红血notothenioids。此外，在背索鱼类中，CTmax与红细胞压积之间存在正相关。我们测试的假设，较低的CTmax的冰鱼是与氧气供应减少。我们采用实验性升温（4 ℃ h（-1）），以确定在常氧和高氧条件下的CTmax，并量化了白血Chaenocephalus aceratus和红血Notothenia coriiceps中氧限制（乳酸水平和缺氧诱导因子-1 α的表达）的相关性。高氧，对应于三至四倍增加海水PO 2，没有延长CTmax在任何物种，尽管整体缓解的血浆和肌肉乳酸盐的上升相比，含氧量正常的治疗。我们的研究结果还表明，心脏HIF-1 α mRNA水平对温度和氧处理的变化不敏感。高氧时CTmax无变化可能代表了氧供应以外的因素对高温下生理衰竭的贡献。
Understanding what limits the capacity of organisms to tolerate increasing temperatures is a critical objective in comparative biology. Using an experimental system of Antarctic notothenioid fishes, we sought to determine whether a mismatch between oxygen demand and oxygen supply was responsible for setting thermal tolerance limits. Previous studies have shown that Antarctic icefishes (family Channichthyidae), which lack hemoglobin, have lower critical thermal maxima (CTmax) than redblooded notothenioids collected from the same region of the Antarctic (Western Antarctic Peninsula). In addition, within the notothenioid fishes there exists a positive correlation between CTmax and hematocrit. We tested the hypothesis that the lower CTmax of icefishes is associated with reduced oxygen supply. We employed an experimental heat ramp (4 degrees C h(-1)) to determine CTmax under both normoxic and hyperoxic conditions and quantified correlates of oxygen limitation (lactate levels and expression of hypoxia-inducible factor-1 alpha) in white-blooded Chaenocephalus aceratus and red-blooded Notothenia coriiceps. Hyperoxia, corresponding to a three- to fourfold increase in seawater PO2, did not extend CTmax in either species despite an overall mitigation in the rise of plasma and muscle lactate compared with the normoxic treatment. Our results also indicate that cardiac HIF-1 alpha mRNA levels were insensitive to changes in both temperature and oxygen treatments. The absence of a change in CTmax with hyperoxia is likely to represent the contribution of factors beyond oxygen supply to physiological failure at elevated temperatures.