SUMMARYAdult 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.

We welcome orginal articles for the trainees' forum on any subject of interest to surgical trainees (maximum 1,500 words). We will also consider letters commenting on articles published in the trainees' forum. Please email articles to bulletin@rcseng.ac.uk.The restrictions placed on training opportunities mean that good-quality teaching is of paramount importance to the modern surgical trainee. The authors of this month's article have constructed a league table of training regions based on success rates of candidates sitting the MRCS examination. They acknowledge that pass rate at examination is only one surrogate measure of training standards and that an objective assessment and ranking of rotations would need to take into account several other factors. Nevertheless, a relatively large variation in performance is evident, which highlights the need for more comprehensive, transparent assessments of the quality of training delivered.Bijan Modarai

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