Gas exchange, ionoregulation and acid-base balance in fish; their interactions and the evolution of complex physiological systems.

鱼类的气体交换、离子调节和酸碱平衡；

• 批准号: RGPIN-2018-04172
• 负责人: Brauner, Colin
• 金额: $ 4.74万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=691330
• 关键词: Gas; exchange; ionoregulation; acid; base

The long-term goal of my research program remains to understand the interaction between gas-exchange, ion regulation and acid-base balance in fish (that represent half of all vertebrates) during environmental acclimation/adaptation and development. In this proposal I will investigate three areas: 1) Teleosts (95% of all fishes) possess a very pH-sensitive hemoglobin (Root effect), where a reduction in pH in specialized structures greatly enhances O2 delivery to the eye and swimbladder which is thought to be associated with the extensive adaptive radiation of teleosts. However, we have discovered a mechanism where a mild acid-base disturbance in the presence of a Root effect and plasma accessible carbonic anhydrase (CA) can double or even triple tissue O2 unloading. We will further investigate the mechanisms involved to permit this system, it's ubiquity among species and its functional significance on whole animal performance. 2) While the gills are the primary site for blood pH regulation in fish, they become limited in this capacity at high CO2 levels. Fish that can tolerate high CO2 appear to abandon blood pH regulation and instead completely defend pHi of important tissues, a fundamentally different pattern from other vertebrates which we have termed preferential pHi (ppHi) regulation. We will investigate the cellular mechanisms for preferential pHi regulation and investigate the hypothesis that it is an embryonic trait in vertebrates that was retained in many fish species (which we propose represents an exaptation for air-breathing in fish) but lost in other adult vertebrates. 3) The vertebrate gill is generally thought to have evolved primarily to enhance gas exchange and secondarily for other processes, such as ionoregulation, acid-base balance and ammonia excretion. However, we have shown that during early development in rainbow trout and lamprey, the gills take on a dominant role for ionoregulation long before gas exchange. We will characterize gill function in basal developing fishes (sturgeon and lamprey), basal chordates (amphioxus and larval tunicates) and a protochordate (acorn worm) at rest and in environments that challenge gas exchange (hypoxia and temperature), ionoregulation (altered water ion levels) and acid-base challenges (elevated water CO2) to shed insight on the plasticity of gill function and provide potential insight into the early evolution of the physiological (non-feeding) role of the chordate gill. The proposed experiments are interdisciplinary, spanning the range of molecular, cellular, and whole animal. They are designed to test novel hypotheses and findings will add significantly to our understanding of the evolution of complex physiological systems. All 3 areas have the potential to alter textbook dogma. Overall this program will train 1 PDF, 5 Ph D, 5 MSc students and 15 undergraduate students.

我的研究计划的长期目标仍然是了解气体交换，离子调节和酸碱平衡之间的相互作用在鱼类（占所有脊椎动物的一半）在环境驯化/适应和发展。在这个建议中，我将调查三个方面：1）硬骨鱼（95%的所有鱼类）具有非常pH敏感的血红蛋白（根效应），其中在专门的结构中pH值的降低大大提高了O2输送到眼睛和鱼鳔，这被认为是与广泛的适应性辐射的硬骨鱼。然而，我们已经发现了一种机制，在存在根效应和血浆可及碳酸酐酶（CA）的情况下，轻度酸碱紊乱可以使组织O2卸载增加一倍甚至三倍。我们将进一步研究允许该系统的机制，它在物种中的普遍性及其对整个动物性能的功能意义。2)虽然鳃是鱼类血液pH值调节的主要部位，但在高CO2水平下，它们的这种能力受到限制。能够耐受高CO2的鱼类似乎放弃了血液pH值调节，而是完全保护重要组织的pH值，这是一种与其他脊椎动物根本不同的模式，我们称之为优先pH值（ppHi）调节。我们将研究优先pHi调节的细胞机制，并研究这是一种在脊椎动物中保留在许多鱼类物种中的胚胎特征（我们提出这代表了鱼类对空气呼吸的适应），但在其他成年脊椎动物中丢失的假设。3)通常认为，脊椎动物鳃的进化主要是为了增强气体交换，其次是为了其他过程，例如离子调节、酸碱平衡和氨排泄。然而，我们已经表明，在虹鳟鱼和七鳃鳗的早期发展过程中，鳃在气体交换之前很久就对离子调节起了主导作用。我们将描述鳃功能在基础发展的鱼类（鲟鱼和七鳃鳗），基索动物（文昌鱼和幼虫被囊动物）和原索动物（橡子虫）在休息和环境中，挑战气体交换（缺氧和温度），离子调节（水离子水平改变）和酸碱挑战（升高的水CO2）来阐明鳃功能的可塑性，并为脊索动物鳃的生理（非摄食）作用的早期进化提供潜在的见解。拟议的实验是跨学科的，跨越分子，细胞和整个动物的范围。它们旨在测试新的假设，发现将大大增加我们对复杂生理系统进化的理解。这三个领域都有可能改变教科书的教条。总体而言，该计划将培养1名PDF，5名博士，5名硕士生和15名本科生。