Lung evolution in vertebrates and the water-to-land transition.
Lung evolution in vertebrates and the water-to-land transition.
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DOI：
10.7554/elife.77156
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发表时间：
2022-07-26
期刊：
影响因子：
7.7
通讯作者：
Brito, Paulo M.
中科院分区：
文献类型：
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作者：
Cupello, Camila;Hirasawa, Tatsuya;Tatsumi, Norifumi;Yabumoto, Yoshitaka;Gueriau, Pierre;Isogai, Sumio;Matsumoto, Ryoko;Saruwatari, Toshiro;King, Andrew;Hoshino, Masato;Uesugi, Kentaro;Okabe, Masataka;Brito, Paulo M.
脊椎动物历史上一个关键的进化变化是古生代（泥盆纪 419-3.59 亿年前）从水到陆的转变，这是由关键的形态和生理变化（包括肺部的获得）所实现的。尽管如此，脊椎动物肺的起源和早期进化仍然存在很大争议，特别是祖先状态是配对还是不配对。由于化石软组织保存的稀缺性，肺的进化只能根据现存的系统发育支架来追踪。在这里，我们首次使用同步加速器 X 射线显微断层扫描和组织学研究了关键活体肺骨鱼广泛发育系列的肺形态。我们的研究结果揭示了脊椎动物肺的原始状态是不配对的，在四足动物的谱系中进化为真正配对的。从水到陆地的转变面临着深刻的生理挑战，成对的肺对于增加表面积、肺顺应性和体积具有决定性作用，尤其是在陆地上呼吸空气时。地球上的所有生命都起源于水下。然而，大约 4 亿年前，一些脊椎动物（例如鱼类）开始发育出四肢和其他特征，使它们能够探索陆地生活。进化中最关键的特征之一是肺部，它赋予脊椎动物在水面上呼吸的能力。大多数陆地脊椎动物，包括人类，都有两个肺，分别位于胸部的两侧。肺部从大气中提取氧气并将其转移到血液中以换取二氧化碳，然后二氧化碳被呼出到大气中。这个重要的器官最初是如何进化的是一个备受争议的话题。这主要是因为肺组织在化石中保存得不好，因此很难追踪脊椎动物的肺在进化过程中是如何变化的。为了克服这一障碍，Cupello 等人。比较了生物的肺部，这对于了解水向陆地转变的早期阶段至关重要。其中包括四种在水面呼吸空气的弓形硬骨鱼和一种生活在陆地上的四足蝾螈。库佩洛等人。使用一系列技术来检查硬骨鱼和蝾螈的肺部在发育过程中如何改变形状。结果表明，脊椎动物的肺最初是一个单一的器官，一旦脊椎动物开始发育四肢，它就在进化过程中真正配对。这种解剖结构的转变增加了可用于交换氧气和二氧化碳的表面积，使脊椎动物可以在陆地上更轻松地呼吸。这些发现为肺部如何进化成当今大多数脊椎动物中发现的配对结构提供了新的见解。这种转变很可能使脊椎动物能够完全适应在水面上呼吸，这可以解释为什么这一事件在进化过程中只发生过一次。
A crucial evolutionary change in vertebrate history was the Palaeozoic (Devonian 419–359 million years ago) water-to-land transition, allowed by key morphological and physiological modifications including the acquisition of lungs. Nonetheless, the origin and early evolution of vertebrate lungs remain highly controversial, particularly whether the ancestral state was paired or unpaired. Due to the rarity of fossil soft tissue preservation, lung evolution can only be traced based on the extant phylogenetic bracket. Here we investigate, for the first time, lung morphology in extensive developmental series of key living lunged osteichthyans using synchrotron x-ray microtomography and histology. Our results shed light on the primitive state of vertebrate lungs as unpaired, evolving to be truly paired in the lineage towards the tetrapods. The water-to-land transition confronted profound physiological challenges and paired lungs were decisive for increasing the surface area and the pulmonary compliance and volume, especially during the air-breathing on land. All life on Earth started out under water. However, around 400 million years ago some vertebrates, such as fish, started developing limbs and other characteristics that allowed them to explore life on land. One of the most pivotal features to evolve was the lungs, which gave vertebrates the ability to breathe above water. Most land-living vertebrates, including humans, have two lungs which sit on either side of their chest. The lungs extract oxygen from the atmosphere and transfer it to the bloodstream in exchange for carbon dioxide which then gets exhaled out in to the atmosphere. How this important organ first evolved is a hotly debated topic. This is largely because lung tissue does not preserve well in fossils, making it difficult to trace how the lungs of vertebrates changed over the course of evolution. To overcome this barrier, Cupello et al. compared the lungs of living species which are crucial to understand the early stages of the water-to-land transition. This included four species of lunged bony fish which breathe air at the water surface, and a four-legged salamander that lives on land. Cupello et al. used a range of techniques to examine how the lungs of the bony fish and salamander changed shape during development. The results suggested that the lungs of vertebrates started out as a single organ, which became truly paired later in evolution once vertebrates started developing limbs. This anatomical shift increased the surface area available for exchanging oxygen and carbon dioxide so that vertebrates could breathe more easily on land. These findings provide new insights in to how the lung evolved into the paired structure found in most vertebrates alive today. It likely that this transition allowed vertebrates to fully adapt to breathing above water, which may explain why this event only happened once over the course of evolution.