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First published online October 18, 2006
Journal of Experimental Biology 209, 4313-4318 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02523

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Contribution of the diaphragmaticus muscle to vital capacity in fasting and post-prandial American alligators (Alligator mississippiensis)

T. J. Uriona^* and C. G. Farmer

Department of Biology, 257 South 1400 East, University of Utah, Salt Lake City, UT 84112, USA

View larger version (27K): [in a new window]   Fig. 1. Illustration of the mechanism of ventilation in crocodilians. (A) Expiration is produced by mediocaudal rotation of the ribs and constriction of the abdominal cavity, which produces a cranial translation of the viscera. Constriction of the abdomen results from activity of the transverses abdominis and the rectus abdominis muscles, which rotate the pubes and gastralia craniodorsad. (B) Inspiration is produced by laterocranial rotation of the ribs and caudal translation of the viscera. The viscera, including the large stomach and liver, are pulled caudad by contraction of the diaphragmaticus muscle. The ischiopubic and ischiotruncus muscles increase the abdominal volume by rotating the pubes and gastralia ventrocaudad. [Figure taken with permission from Farmer and Carrier (Farmer and Carrier, 2000).]

View larger version (4K): [in a new window]   Fig. 2. Sample recordings of ventilation during 5% hypercapnic anoxic treatment from two post-prandial American alligators. (A) Data from an alligator with a transected diaphragmaticus (body mass 93 g). (B) Data from a control alligator (body mass 94 g). A breath cycle normally begins with an exhalation, followed by an inhalation and subsequent apnea. Expiration and inspiration occur when the trace is above and below the solid line (zero marker for airflow), respectively. The beginning of inspiration has been aligned to better illustrate the difference between the animals in both time to inspire and breath size. Calibration bar, 1 s.

View larger version (9K): [in a new window]   Fig. 3. Study 1. Components of the maximum inhalation that occurred when the animals inspired a 5% hypercapnic anoxic gas over a 3-min period. (A) Relative vital capacity (mean ± s.e.m.). (B) Relative maximum flow (mean ± s.e.m.). (C) Duration of inhalation (mean ± s.e.m.). C Fast, fasting control alligators; C PP, post-prandial control alligators; D Fast and D PP, alligators that had the diaphragmaticus muscle transected and were in the fasting and post-prandial state, respectively. Significant difference (P0.05; t-test) between fasting and post-prandial states within the control group (N=5); significant difference (P0.05; t-test) between fasting and post-prandial states within the experimental group (N=5); *significant difference (P0.05; t-test) between experimental and control alligators during post-prandial treatment.

View larger version (10K): [in a new window]   Fig. 4. Study 2. The relative vital capacity (mean ± s.e.m.) of animals breathing a 5% hypercapnic-anoxic or normoxia gas for a 3 min period at 1 week, 2 weeks, 2 months and 6 months after the surgery (trials 1, 2, 3 and 4, respectively). S Fast, fasting sham operated alligators; S PP, post-prandial sham operated alligators; D Fast and D PP, alligators that had the diaphragmaticus muscle transected, and were in the fasting and post-prandial state, respectively. Significant difference (P0.05, t-test) between fasting and post-prandial states within the sham group (N=3); significant difference (P0.05; t-test) between fasting and post-prandial states within the experimental group (N=3); *significant difference between experimental and control alligators (P0.05, t-test) during post-prandial treatment.