Bay Paul Centre, Marine Biological Laboratory, Woods Hole, MA, USA.
Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
J Comp Physiol B. 2024 Oct;194(5):557-568. doi: 10.1007/s00360-024-01545-5. Epub 2024 Mar 26.
Gill function in gas exchange and ion regulation has played key roles in the evolution of fishes. In this review, we summarize data from the fields of palaeontology, developmental biology and comparative physiology for when and how the gills first acquired these functions. Data from across disciplines strongly supports a stem vertebrate origin for gas exchange structures and function at the gills with the emergence of larger, more active fishes. However, the recent discovery of putative ionocytes in extant cephalochordates and hemichordates suggests that ion regulation at gills might have originated much earlier than gas exchange, perhaps in the ciliated pharyngeal arches in the last common ancestor of deuterostomes. We hypothesize that the ancestral form of ion regulation served a filter-feeding function in the ciliated pharyngeal arches, and was later coopted in vertebrates to regulate extracellular ion and acid-base balance. We propose that future research should explore ionocyte homology and function across extant deuterostomes to test this hypothesis and others in order to determine the ancestral origins of ion regulation in fish gills.
鱼类的气体交换和离子调节中的鳃功能在其进化过程中发挥了关键作用。在这篇综述中，我们总结了古生物学、发育生物学和比较生理学领域的数据，以了解鳃最初是在何时以及如何获得这些功能的。来自不同学科的数据强烈支持了气体交换结构和功能的脊椎动物起源，最早出现在更大、更活跃的鱼类中。然而，最近在现存的半索动物和脊索动物中发现了假定的离子细胞，这表明离子调节可能比气体交换更早起源，也许起源于后口动物的最后共同祖先的纤毛咽弓中。我们假设，离子调节的祖先是在纤毛咽弓中起滤食作用的，后来在脊椎动物中被用来调节细胞外离子和酸碱平衡。我们建议，未来的研究应该探索现存的后口动物中的离子细胞同源性和功能，以检验这一假设和其他假设，从而确定鱼类鳃中离子调节的祖源。
