| Morphometrics of the avian small intestine compared with that of nonflying mammals: a phylogenetic approach. | |
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MedLine Citation:
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PMID: 18754728 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Flying animals may experience a selective constraint on gut volume because the energetic cost of flight increases and maneuverability decreases with greater digesta load. The small intestine is the primary site of absorption of most nutrients (e.g., carbohydrates, proteins, fat) in both birds and mammals. Therefore, we used a phylogenetically informed approach to compare small intestine morphometric measurements of birds with those of nonflying mammals and to test for effects of diet within each clade. We also compared the fit of nonphylogenetic and phylogenetic models to test for phylogenetic signal after accounting for effects of body mass, clade, and/or diet. We provide a new MATLAB program (Regressionv2.m) that facilitates a flexible model-fitting approach in comparative studies. As compared with nonflying mammals, birds had 51% less nominal small intestine surface area (area of a smooth bore tube) and 32% less volume. For animals <365 g in body mass, birds also had significantly shorter small intestines (20%-33% shorter, depending on body mass). Diet was also a significant factor explaining variation in small intestine nominal surface area of both birds and nonflying mammals, small intestine mass of mammals, and small intestine volume of both birds and nonflying mammals. On the basis of the phylogenetic trees used in our analyses, small intestine length and nominal surface area exhibited statistically significant phylogenetic signal in birds but not in mammals. Thus, for birds, related species tended to be similar in small intestine length and nominal surface area, even after accounting for relations with body mass and diet. A reduced small intestine in birds may decrease the capacity for breakdown and active absorption of nutrients. Birds do not seem to compensate for reduced digestive and absorptive capacity via a longer gut retention time of food, but we found some evidence that birds have an increased mucosal surface area via a greater villus area, although not enough to compensate for reduced nominal surface area. We predict that without increased rate of enzyme hydrolysis and/or mediated transport and without increased passive absorption of water-soluble nutrients, birds may operate with a reduced digestive capacity, compared with that of nonflying mammals, to meet an increase in metabolic needs (i.e., a reduced spare capacity). |
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Authors:
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Shana R Lavin; William H Karasov; Anthony R Ives; Kevin M Middleton; Theodore Garland |
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Publication Detail:
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Type: Comparative Study; Journal Article |
Journal Detail:
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Title: Physiological and biochemical zoology : PBZ Volume: 81 ISSN: 1537-5293 ISO Abbreviation: Physiol. Biochem. Zool. Publication Date: 2008 Sep-Oct |
Date Detail:
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Created Date: 2008-09-16 Completed Date: 2008-12-08 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 100883369 Medline TA: Physiol Biochem Zool Country: United States |
Other Details:
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Languages: eng Pagination: 526-50 Citation Subset: IM |
Affiliation:
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Department of Wildlife Ecology, University of Wisconsin, Madison, Wisconsin 53706, USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Birds / anatomy & histology*, genetics Body Weights and Measures Intestine, Small / anatomy & histology* Mammals / anatomy & histology*, genetics Models, Biological* Phylogeny* Regression Analysis Software* Species Specificity |
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