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The digestive adaptation of flying vertebrates: High intestinal paracellular absorption compensates for smaller guts

Caviedes-Vidal, E., Mcwhorter, T., Lavin, S., Chediak, J., Tracy, Christopher and Karasov, W. (2007). The digestive adaptation of flying vertebrates: High intestinal paracellular absorption compensates for smaller guts. Proceedings of the National Academy of Sciences of USA,104(48):19132-19137.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 39 times in Scopus Article | Citations

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IRMA ID 78672763xPUB20
Title The digestive adaptation of flying vertebrates: High intestinal paracellular absorption compensates for smaller guts
Author Caviedes-Vidal, E.
Mcwhorter, T.
Lavin, S.
Chediak, J.
Tracy, Christopher
Karasov, W.
Journal Name Proceedings of the National Academy of Sciences of USA
Publication Date 2007
Volume Number 104
Issue Number 48
ISSN 0027-8424   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-37648998884
Start Page 19132
End Page 19137
Total Pages 6
Place of Publication United States of America
Publisher National Academy of Sciences
Field of Research 0606 - Physiology
HERDC Category C1 - Journal Article (DEST)
Abstract Anecdotal evidence suggests that birds have smaller intestines than mammals. In the present analysis, we show that small birds and bats have significantly shorter small intestines and less small intestine nominal (smooth bore tube) surface area than similarly sized nonflying mammals. The corresponding >50% reduction in intestinal volume and hence mass of digesta carried is advantageous because the energetic costs of flight increase with load carried. But, a central dilemma is how birds and bats satisfy relatively high energy needs with less absorptive surface area. Here, we further show that an enhanced paracellular pathway for intestinal absorption of water-soluble nutrients such as glucose and amino acids may compensate for reduced small intestines in volant vertebrates. The evidence is that l-rhamnose and other similarly sized, metabolically inert, nonactively transported monosaccharides are absorbed significantly more in small birds and bats than in nonflying mammals. To broaden our comparison and test the veracity of our finding we surveyed the literature for other similar studies of paracellular absorption. The patterns found in our focal species held up when we included other species surveyed in our analysis. Significantly greater amplification of digestive surface area by villi in small birds, also uncovered by our analysis, may provide one mechanistic explanation for the observation of higher paracellular absorption relative to nonflying mammals. It appears that reduced intestinal size and relatively enhanced intestinal paracellular absorption can be added to the suite of adaptations that have evolved in actively flying vertebrates.
DOI http://dx.doi.org/10.1073/pnas.0703159104   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
 
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