Collaborative Research: The Physiological and Biochemical Underpinnings of Thermal Tolerance in Antarctic Notothenioid Fishes

南极洲周围的海洋是一群非同寻常的鱼类的家园，由一种非常适合在冰冷水域生活的鱼类主导，它们在那里具有重要的生态意义。令人极为关切的是，随着南极半岛西部地区升温的速度比南半球其他任何地区都快，这些鱼类抵御气温上升的能力如何。有一种被称为冰鱼的南极鱼类特别容易受到气温上升的影响，因为与地球上所有其他脊椎动物不同，冰鱼是白血动物，因为它们缺乏氧气结合蛋白血红蛋白。与南极红血鱼相比，这极大地降低了它们向组织运输和输送氧气的能力。此前的研究表明，冰鱼对气温升高的耐受性确实较差，但潜在的因素完全未知。此外，目前还不清楚南极的红血或白血鱼类是否能适应或适应气温的适度上升，类似于这些动物在地球变暖时可能经历的温度变化。研究人员将确定心脏功能和/或神经系统功能是否限制了南极鱼类的耐热性，并将确定它们适应更温暖温度的能力。该项目将通过培养研究生和本科生来推进NSF培养新一代科学家的目标。此外，该项目将与一名高中生物教师合作，该教师来自一所主要服务于少数族裔学生的学校。学生们将学习有关海洋环境的知识，并将建造一台用于野外的相机，以了解更多关于南极鱼类的知识。两名学生和这位老师还将参加夏季海洋生物实习项目。南极鱼类属于Notothenioidei亚目(称为Notothenioidae)，是地球上最不能适应温度变化的生物之一。与红血鱼相比，无血红蛋白的冰鱼承受温度变化的能力更差。虽然这一点已经得到了很好的证明，但其潜在的生理和生化机制尚不清楚。研究人员将验证这样的假设：与红血物种相比，冰鱼的心脏功明显更大，而且随着温度的升高，冰鱼的心功更大，再加上血液携氧能力降低，与红血物种相比，在较低的温度下会导致心力衰竭。他们还假设，神经元功能限制了热血三叉神经的耐热性。这些假说将通过各种实验进行检验。例如，研究人员将同时测量心率和临界最高热值。他们还将利用各种技术表征代谢和基因表达对温度升高的反应，并确定线粒体功能是否有助于耐热性。为了确定神经元功能是否限制了热耐受，他们将量化整个动物对变暖的行为反应，以及只对大脑区域变暖的行为反应。他们还将确定适应较高温度是否会影响心脏功能，并将测量中央代谢途径中各种酶的活性。

The ocean surrounding Antarctica is home to an extraordinary assemblage of fishes, dominated by a single group that are extremely well-suited to life in icy waters and which are of significant ecological importance there. Of great concern is the capacity of these fishes to withstand increases in temperature as the region of the Western Antarctic Peninsula warms at a rate faster than any other area in the Southern hemisphere. One particular group of Antarctic fishes, known as the icefishes, are particularly vulnerable to increases in temperature because unlike all other vertebrates on earth, icefishes are white-blooded due to their lack of the oxygen-binding protein hemoglobin. This greatly reduces their capacity to transport and deliver oxygen to tissues compared to red-blooded Antarctic fishes. Previous studies have shown that icefishes are indeed less tolerant to elevations in temperature but the underlying factors are completely unknown. Additionally, it is not understood if red- or white-blooded Antarctic fishes can adjust, or acclimate, to modest increases in temperature, similar to those changes in temperature the animals might experience as the earth warms. The investigators will determine if heart function and/or nervous system function limits thermal tolerance of Antarctic fishes, and will determine their capacity to acclimate to warmer temperatures. The project will further the NSF goal of training new generations of scientists by training graduate and undergraduate students. In addition, the project will collaborate with a high school biology teacher from a school which serves a largely minority student body. The students will learn about the marine environment, and will construct a camera to be used in the field to learn more about Antarctic fishes. Two students and the teacher will also attend a summer marine biology internship program.Antarctic fishes within the suborder Notothenioidei (called "notothenioids") are among the organisms on earth least able to deal with changes in temperature. The hemoglobinless icefish are even less able to withstand temperature changes than are red-blooded notothenioids. While this is well documented, the underlying physiological and biochemical mechanisms responsible are unknown. The investigators will test the hypotheses that cardiac work is significantly greater in icefishes compared to red-blooded species, and that as temperature increases, the greater cardiac work of icefishes, coupled with reduced blood oxygen-carrying capacity, results in cardiac failure at a lower temperature compared to red-blooded species. They also hypothesize that neuronal function limits thermal tolerance of red-blooded notothenioids. These hypotheses will be tested using a wide variety of experiments. For example, the investigators will measure heart rate concurrently with critical thermal maximum. They will also characterize metabolic and gene-expression responses to elevated temperature and determine if mitochondrial function contributes to thermal tolerance using a variety of techniques. To determine if neuronal function limits thermal tolerance they will quantify behavioral responses to warming of whole animals and to warming of only the brain area. They will also determine if acclimation to warmer temperatures impacts heart function and they will measure activities of a variety of enzymes from central metabolic pathways.