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Alligators and crocodiles have high paracellular nutrient absorption, but differ in digestive morphology and physiology

Tracy, Christopher R., McWhorter, Tood J., Gienger, Christopher, Starck, J. Matthias, Medley, Peter, Manolis, S. Charlie, Webb, Grahame and Christian, Keith A. (2015). Alligators and crocodiles have high paracellular nutrient absorption, but differ in digestive morphology and physiology. In: SICB Annual Meeting 2015, Florida, USA, 3-7 January 2015.

Document type: Conference Paper
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IRMA ID 75039815xPUB999
Author Tracy, Christopher R.
McWhorter, Tood J.
Gienger, Christopher
Starck, J. Matthias
Medley, Peter
Manolis, S. Charlie
Webb, Grahame
Christian, Keith A.
Title Alligators and crocodiles have high paracellular nutrient absorption, but differ in digestive morphology and physiology
Conference Name SICB Annual Meeting 2015
Conference Location Florida, USA
Conference Dates 3-7 January 2015
Conference Publication Title Published in: Integrative and Comparative Biology
Place of Publication United Kingdom
Publisher Oxford University Press
Publication Year 2015
Volume Number 55
Issue Number 6
ISSN 1557-7023   (check CDU catalogue open catalogue search in new window)
Start Page 986
End Page 1004
Total Pages 19
HERDC Category E1 - Conference Publication (DIISR)
Abstract Much of what is known about crocodilian nutrition and growth has come from animals propagated in captivity, but captive animals from the families Crocodilidae and Alligatoridae respond differently to similar diets. Since there are few comparative studies of crocodilian digestive physiology to help explain these differences, we investigated young Alligator mississippiensis and Crocodylus porosus in terms of (1) gross and microscopic morphology of the intestine, (2) activity of the membrane-bound digestive enzymes aminopeptidase-N, maltase, and sucrase, and (3) nutrient absorption by carrier-mediated and paracellular pathways. We also measured gut morphology of animals over a larger range of body sizes. The two species showed different allometry of length and mass of the gut, with A. mississippiensis having a steeper increase in intestinal mass with body size, and C. porosus having a steeper increase in intestinal length with body size. Both species showed similar patterns of magnification of the intestinal surface area, with decreasing magnification from the proximal to distal ends of the intestine. Although A. mississippiensis had significantly greater surface-area magnification overall, a compensating significant difference in gut length between species meant that total surface area of the intestine was not significantly different from that of C. porosus . The species differed in enzyme activities, with A. mississippiensis having significantly greater ability to digest carbohydrates relative to protein than did C. porosus . These differences in enzyme activity may help explain the differences in performance between the crocodilian families when on artificial diets. Both A. mississippiensis and C. porosus showed high absorption of 3-O methyl d -glucose (absorbed via both carrier-mediated and paracellular transport), as expected. Both species also showed surprisingly high levels of l -glucose-uptake (absorbed paracellularly), with fractional absorptions as high as those previously seen only in small birds and bats. Analyses of absorption rates suggested a relatively high proportional contribution of paracellular (i.e., non-mediated) uptake to total uptake of nutrients in both species. Because we measured juveniles, and most paracellular studies to date have been on adults, it is unclear whether high paracellular absorption is generally high within crocodilians or whether these high values are specific to juveniles.
Additional Notes doi:10.1093/icb/icv060
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