Respiratory biology of diving in the sea turtle

The sea turtle is habitually submarine, surfacing only briefly to breathe. Aquatic respiration is negligible in the loggerhead (Caretta caretta), accounting for less than 2% of the resting oxygen consumption. Unlike most marine mammals there are no special adaptations for increased oxygen capacity in blood or tissue. The lung, however, functions as the major oxygen store, and calculations indicate that it can supply sufficient oxygen for most routine dives (up to 20 min) to be aerobic. The respiratory properties of sea turtle blood are particularly well suited to lung-tissue transport during routine breahhold periods. Sea turtles survive prolonged dives of at least 3 h by having a high anaerobic capacity. Substantial changes in blood gas and pH levels are endured and special adaptations in brain energy metabolism are indicated.