Pharyngeal breathing in softshell turtles

Turtles breath air, right?  No turtles have gills, right?  These statements are correct, but you may be surprised to learn that some turtles can remain under water for several hours and others possibly indefinitely.

Most aquatic reptiles can slow all metabolic processes that sharply lowers their oxygen needs.  Many turtles that hibernate underwater have within their cloaca (a common opening for the excretory, alimentary and reproductive systems) a pair of small pockets (called cloacal bursae) that remove oxygen from circulating water.  This system seems to work well since mud turtles have been observed sitting quiescently on pond bottoms for hours.

The most spectacular adaptation, however, appears in the soft-shelled turtles (Apalone sp.) of which there are two local species.  These turtles derive their common name from the absence of horny scutes on their shells.  They are the most highly aquatic turtles in our area and they can remain alert while obtaining l00% of their oxygen needs from their surroundings.  Seventy percent of their oxygen is absorbed through their skin.  The other 30% results from pumping water in and out of the pharynx (throat) where there are many little projections of tisuse having small blood vessels.  These “villi” provide a greater surface area for oxygen absorption.