Can turtles breathe through their butts?
Turtles have a single rear vent that is referred to as a cloaca. Feces, urine, and eggs all exit a turtle through this cloaca, so not surprisingly it is quite elastic and the opening can stretch considerably. In a small number of water turtles, the cloaca also possesses a pair of well-developed, vascularized sacs that lead off it called bursae. These cloacal bursae are surrounded by the same thin membrane as the rest of the cloaca. Gas exchange can occur across this membrane when a turtle is submerged and allow some oxygen to reach the blood. In most species this makes a minor contribution to respiration however one species of turtle from Australia has taken this to extremes. The Fitzroy River turtle (Rheodytes leukops) can pump water in and out of its cloacal bursae such that it can obtain as much as two-thirds of its oxygen supply through this route. [Source: Aquatic respiration and diving in the freshwater turtle, Rheodytes leukops by Craig E. Franklin. Proc. Physiol. Soc.] Michael
