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

南极洲周围的海洋是一个非凡的鱼类组合的家园，由一个非常适合在冰冷的沃茨生活的单一群体主导，并且具有重要的生态重要性。最令人关注的是这些鱼类承受温度上升的能力，因为南极半岛西部地区的变暖速度比南半球任何其他地区都快。南极鱼类中的一个特殊群体，被称为冰鱼，特别容易受到温度升高的影响，因为与地球上所有其他脊椎动物不同，冰鱼是白血的，因为它们缺乏氧结合蛋白血红蛋白。这大大降低了他们的运输能力和提供氧气的组织相比，热血南极鱼。先前的研究表明，冰鱼确实对温度升高的耐受性较低，但其潜在因素完全未知。此外，还不清楚红血或白血南极鱼是否能适应或适应温度的适度升高，类似于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高温度的能力。 该项目将通过培训研究生和本科生来进一步实现NSF培养新一代科学家的目标。 此外，该项目将与一所主要为少数民族学生服务的学校的高中生物教师合作。学生们将了解海洋环境，并将建造一个相机在现场使用，以了解更多关于南极鱼类。两名学生和老师还将参加一个夏季海洋生物实习项目。南极鱼类属于南极鱼亚目（称为“南极鱼”），是地球上最不适应温度变化的生物之一。没有血红蛋白的冰鱼甚至比红血的南极鱼更不能承受温度的变化。虽然这是有据可查的，但其潜在的生理和生化机制尚不清楚。研究人员将测试这样的假设，即与红血物种相比，冰鱼的心脏工作显着更大，并且随着温度的升高，冰鱼的心脏工作更大，再加上血液携氧能力降低，导致心力衰竭与红血物种相比，温度较低。他们还假设神经元功能限制了红血类背鳍动物的热耐受性。这些假设将使用各种各样的实验进行测试。例如，研究者将在临界热最大值的同时测量心率。他们还将表征代谢和基因表达对高温的反应，并使用各种技术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性，他们将量化整个动物变暖和仅大脑区域变暖的行为反应。他们还将确定适应更温暖的温度是否会影响心脏功能，并将测量来自中央代谢途径的各种酶的活性。

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.