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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=646192
• 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鱼类(占所有脊椎动物的一半)在环境适应/适应和发育过程中气体交换、离子调节和酸碱平衡之间的相互作用。在这项提案中，我将研究三个方面：1)硬骨鱼(占所有鱼类的95%)拥有一种对pH非常敏感的血红蛋白(根效应)，在这种情况下，特殊结构中pH的降低极大地增强了向眼睛和泳囊的氧气输送，这被认为与硬骨鱼的广泛适应辐射有关。然而，我们已经发现了一种机制，在根效应和血浆可及性碳酸酐酶(CA)存在的情况下，轻微的酸碱失衡可以使组织的O2负荷增加一倍甚至三倍。我们将进一步研究允许这个系统的机制，它在物种中的普遍存在，以及它对整个动物性能的功能意义。2)虽然鳃是鱼类血液pH调节的主要部位，但在高二氧化碳水平下，它们的这一能力变得有限。能够耐受高二氧化碳的鱼类似乎放弃了血液pH调节，转而完全防御重要组织的phi，这与其他脊椎动物的模式完全不同，我们称之为优先phi(PpHi)调节。我们将研究优先调节phi的细胞机制，并调查这一假设，即它是脊椎动物的胚胎特征，在许多鱼类物种中保留(我们认为这代表鱼类呼吸空气的突起)，但在其他成年脊椎动物中丢失。3)脊椎动物的鳃通常被认为主要是为了加强气体交换，其次是为了其他过程，如离子调节、酸碱平衡和排氨。然而，我们已经证明，在虹鲑鱼和七鳃鳗的早期发育过程中，在气体交换之前很久，鳃就承担了离子调节的主导角色。我们将在静止和挑战气体交换(缺氧和温度)、离子调节(改变水离子水平)和酸碱挑战(水二氧化碳升高)的环境中，研究基本发育的鱼类(鲟鱼和七鳃鳗)、基本脊索动物(文昌鱼和幼体被膜)和原索动物(橡子虫)的鳃功能，以深入了解鳃功能的可塑性，并为脊索鳃的生理(非摄食)作用的早期进化提供潜在的洞察力。拟议的实验是跨学科的，跨越分子、细胞和整个动物的范围。它们被设计用来检验新的假说，而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上的教条。总体来说，该项目将培养1名博士、5名博士、5名硕士和15名本科生。