The pelvis of crocodilians is highly derived in that the pubic bones are isolated from the acetabulum and are attached to the ischia via moveable joints. We examined the possible role of this unusual morphology in lung ventilation by measuring ventilation, abdominal pressure and the electrical activity of several abdominal and pelvic muscles in the American alligator (Alligator mississippiensis). We found that the activity of two pelvic muscles, the ischiopubis and ischiotruncus muscles, was correlated with inspiration; these muscles rotate the pubes ventrally and thereby increase abdominal volume. During expiration, contraction of the rectus abdominis and transversus abdominis rotates the pubes dorsally. We suggest that this mechanism facilitates diaphragmatic breathing by creating space for caudal displacement of the viscera during inspiration. Because birds also use a dorso-ventral movement of the pelvis to effect ventilation, some form of pelvic aspiration may be plesiomorphic for archosaurs.
JOURNAL ARTICLE|
01 June 2000
Pelvic aspiration in the American alligator (Alligator mississippiensis)
C.G. Farmer,
C.G. Farmer
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
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D.R. Carrier
D.R. Carrier
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
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C.G. Farmer
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
D.R. Carrier
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
Online Issn: 1477-9145
Print Issn: 0022-0949
© 2000 by Company of Biologists
2000
J Exp Biol (2000) 203 (11): 1679–1687.
Citation
C.G. Farmer, D.R. Carrier; Pelvic aspiration in the American alligator (Alligator mississippiensis). J Exp Biol 1 June 2000; 203 (11): 1679–1687. doi: https://doi.org/10.1242/jeb.203.11.1679
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