The importance of the M. diaphragmaticus to the duration of dives in the American alligator (Alligator mississippiensis) |
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| Authors: | Todd J Uriona Melissa Lyon CG Farmer |
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| Institution: | 1. Wildlife Health and Conservation Centre, University of Sydney, Camden, NSW, Australia;2. Hartleys Crocodile Adventures, Wangetti via Cairns, QLD, Australia;3. Wildlife Conservancy of Tropical Queensland, Cairns, QLD, Australia;4. Sydney University Rural Veterinary Centre, Camden, NSW, Australia;1. Department of Animal Sciences, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa;2. School of Animal Biology M085, Faculty of Natural and Agricultural Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;3. Directorate Animal Sciences: Oudtshoorn, PO Box 351, Oudtshoorn 6620, South Africa;4. Directorate Animal Sciences: Elsenburg, Private Bag X1, Elsenburg 7607, South Africa;1. Department of Pediatrics, Section of Emergency Medicine, Yale School of Medicine, New Haven, Conn;2. Department of Pediatrics, Section of Emergency Medicine, Children''s Hospital Colorado, University of Colorado School of Medicine, Aurora, Colo;3. Department of Pediatrics, Section of Pediatric Emergency Medicine, Children''s Hospital of Wisconsin, Medical College of Wisconsin, Milwaukee, Wis;1. Department of Anaesthesiology and Intensive Care, National Institute of Oncology;2. Department of Thoracic Surgery, National Institute of Oncology;3. Thoracic Surgery Department on the base of National Institute of Oncology, Semmelweis University;4. Medical University of Vienna;1. Department of Thoracic and Cardiovascular Surgery, West-German Heart Center Essen, University Duisburg-Essen, Essen, Germany;2. Hatter Cardiovascular Institute, London, United Kingdom, and Department of Internal Medicine, The Cleveland Clinic, Cleveland, Ohio |
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| Abstract: | We tested the hypothesis that the crocodilian M. diaphragmaticus extends the duration of dives by disabling this muscle in a group of juvenile American alligators and comparing the duration of their dives to the duration of the dives of animals in which the muscle remained intact. We studied the groups while they were fasting, 1 h after they had eaten a meal with a density that was either greater or less than water, and at 22 and 28 °C. We found that the duration of dives was longer for the control group compared to animals without a functional M. diaphragmaticus, both when fasting and after having consumed the denser meal. The warmer temperature significantly decreased the duration of the dives for both groups, as did eating in general. The preponderance of these data indicates that transection of the diaphragmaticus reduced time spent underwater, but the mechanism for this reduction is unknown. Lack of a functional diaphragmaticus could impair the animals’ ability to inspire sufficient air to support the dive, but we think this explanation is unlikely because both groups were able to float at the surface and thus needed to reduce lung volume to dive. An alternative explanation is that the effect on duration is a consequence of an impairment of a locomotor rather than ventilatory function of the muscle. |
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