Researchers interested in the evolution of air breathing in bony fishes (Osteicthyes) recently published a fascinating review in the Physiologist. The ability to breathe air made life on land as we know it possible. What is interesting though is that the ability to breathe air actually evolved independently possibly 38-67 times in history. Currently, there are over 400 air-breathing fishes belonging to the Sarcopterygii and Actinopterygii classes.
To adapt to life on land, animals had to develop stronger bones to handle the force of gravity and new ways of getting from one place to another; different ways to find food; the ability to regulate water, ion and pH balance; reproduction in a dry environment; the ability to exchange gases with the air around them; and variations in sensory physiology. It is believed that the first terrestrial adventurers were already breathing air in their aquatic homes. Simply put, the transition was rather complicated. Maybe we need to institute a fish appreciation week for life as we know it…
Bayley M, Damsgaard C, Thomsen M, Malte H, Wang T. Learning to Air-Breathe: The First Steps. Physiology 34(1): 14-29, 2018. https://doi.org/10.1152/physiol.00028.2018
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