Lungs
All lungfish have two lungs, with the exception of the Australian lungfish, which only has one. The lung(s) connect to the pharynx. The lungs of lungfish are homologous to the lungs of tetrapods. As in tetrapods and bichirs, the lungs extend from the ventral surface of the esophagus and gut.
While other species of fish can breathe air via modified, vascularized gas bladders, these bladders are usually simple sacs, devoid of complex internal structure. In contrast, the lungs of lungfish are subdivided into numerous smaller air sacs, maximizing the surface area available for gas exchange.
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