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First published online October 16, 2009
Journal of Experimental Biology 212, 3440-3447 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.034991

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Ontogenetic changes in tracheal structure facilitate deep dives and cold water foraging in adult leatherback sea turtles

John Davenport^1,4,*, John Fraher², Ed Fitzgerald³, Patrick McLaughlin³, Tom Doyle^1,4, Luke Harman¹, Tracy Cuffe² and Peter Dockery⁵

¹ Department of Zoology, Ecology and Plant Science and Environmental Research Institute, University College Cork, Distillery Fields, North Mall, Cork, Ireland
² Department of Anatomy, University College Cork, College Road, Cork, Ireland
³ Radiology Department, Mercy Hospital, Cork, Ireland
⁴ Coastal and Marine Resources Centre, University College Cork, Naval Base, Haulbowline, Cork, Ireland
⁵ Department of Anatomy National University of Ireland, Galway, University Road, Galway, Ireland

^* Author for correspondence (j.davenport{at}ucc.ie)

Accepted 5 August 2009

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.

Key words: Leatherback turtle, Dermochelys, tracheal structure, vascular plexus, diving, gigantothermy

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