Sensory innervation of the Gills: O2-sensitive chemoreceptors and mechanoreceptors

Physical characteristics of water (O2 solubility and capacitance) dictate that cardiovascular and ventilatory performance be controlled primarily by the need for oxygen uptake rather than carbon dioxide excretion, making O2 receptors more important in fish than in terrestrial vertebrates. An understanding of the anatomy and physiology of mechanoreception and O2 chemoreception in fishes is important, because water breathing is the primitive template upon which the forces of evolution have modified into the various cardioventilatory modalities we see in extant terrestrial species. Key to these changes are the O2-sensitive chemoreceptors and mechanoreceptors, their mechanisms and central pathways.