Abstract
The difficulty in obtaining oxygen from many aquatic environments has led to the frequent evolution of air breathing among fishes. Among several groups of fish, elements of the gastrointestinal (GI) tract have been exploited to extract oxygen from the air and have become air-breathing organs (ABOs). Despite the perceived difficulties in balancing digestive and respiratory function, gut air breathing (GAB) in fishes has evolved multiple times and GAB fishes have become very successful. The modification of esophagus, stomach, or intestine into ABOs always involved increased vascularization with capillaries embedded in the epithelium close enough to inspired air for significant O 2 diffusion to occur. The gut wall in ABOs has generally undergone substantial reduction, is separated from digestive portions of the GI tract with sphincters and is capable of producing surfactant. GAB fishes tend to be facultative air breathers that use air breathing to supplement aquatic respiration in hypoxic waters, but some hindgut breathers also appear to be continuous, but not obligate, air breathers.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call