This is used in various species as an alternative respiration mechanism in hypoxic environments as a means to supplement blood oxygen.
[2] They accomplish this by having a pair of accessory air bladders connected to the cloaca which can absorb oxygen from the water.
[4] The pond loach is able to respond to the periodic drying in their native habitats by burrowing into the mud and exchanging gas through the posterior end of their alimentary canal.
[5][6] Studies have shown that mammals are capable of performing intestinal respiration to a limited degree in a laboratory setting.
In 2024 Ig Nobel Prize an award in physiology has been given to a study proving that pigs are capable of this as well.