The vascular lining in the trachea of adult leatherback sea turtles helps them maintain body temperature while foraging in cold water via counter-current exchange.


“Adult leatherbacks are large animals (300–500 kg), overlapping in size with marine pinniped and cetacean species. Unlike marine mammals, they start their aquatic life as 40–50 g hatchlings, so undergo a 10,000-fold increase in body mass during independent existence. Hatchlings are limited to the tropics and near-surface water. Adults, obligate predators on gelatinous plankton, encounter cold water at depth (<1280 m) or high latitude and are gigantotherms that maintain elevated core body temperatures in cold water. This study shows that there are great ontogenetic changes in tracheal structure related to diving and exposure to cold. Hatchling leatherbacks have a conventional reptilian tracheal structure with circular cartilaginous rings interspersed with extensive connective tissue. The adult trachea is an almost continuous ellipsoidal cartilaginous tube composed of interlocking plates, and will collapse easily in the upper part of the water column during dives, thus avoiding pressure-related structural and physiological problems. It is lined with an extensive, dense erectile vascular plexus that will warm and humidify cold inspired air and possibly retain heat on expiration. A sub-luminal lymphatic plexus is also present. Mammals and birds have independently evolved nasal turbinates to fulfil such a respiratory thermocontrol function; for them, turbinates are regarded as diagnostic of endothermy. This is the first demonstration of a turbinate equivalent in a living reptile.” (Davenport et al. 2009:3440)

“[T]he trachea is lined throughout by a continuous vascular plexus. This contains a high proportion of longitudinally arranged, large-diameter blood vessels lying mainly in the deeper two-thirds of the mucosa, with prominent cross-connections between them. The arrangement is consistent with their functioning as a counter-current arrangement, retaining heat and maintaining body temperatureWe believe that the vascular lining of the long adult leatherback trachea functions in analogous fashion to nasal turbinates.” (Davenport et al. 2009:3445-6)

Journal article
Ontogenetic changes in tracheal structure facilitate deep dives and cold water foraging in adult leatherback sea turtlesJournal of Experimental BiologyFebruary 20, 2017
J. Davenport, J. Fraher, E. Fitzgerald, P. McLaughlin, T. Doyle, L. Harman, T. Cuffe, P. Dockery

Leatherback Sea TurtleDermochelys coriaceaSpecies