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Allometry of paracellular absorption in birds
Shana R Lavin1, William H Karasov
1Department of Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. slavin@lpzoo.org.
Physiological and Biochemical Zoology : PBZ
|August 30, 2008
Summary
Small birds absorb more nutrients through paracellular pathways to compensate for shorter intestines. This nutrient absorption method is inversely related to body mass in birds.
Area of Science:
- Comparative physiology
- Avian biology
- Gastrointestinal absorption
Background:
- Nutrient absorption occurs via transcellular and paracellular routes.
- Small birds (<180 g) exhibit greater paracellular glucose absorption than mammals.
- This may compensate for reduced mass-corrected intestinal length in small birds.
Purpose of the Study:
- To investigate the relationship between avian body mass and paracellular absorption.
- To test if larger birds have paracellular absorption comparable to nonflying mammals.
Main Methods:
- Measured absorption of inert carbohydrate probes in heavy bird species (>300 g).
- Included diverse taxa: American coots, mallards, pheasants, and pigeons.
- Utilized consistent methodology across all species.
Main Results:
- Carbohydrate probe absorption showed an inverse relationship with body mass in birds.
- Large birds (>500 g) exhibited paracellular absorption levels similar to nonflying mammals.
- Smaller avian species demonstrated higher paracellular uptake.
Conclusions:
- Avian paracellular absorption is inversely correlated with body mass.
- This mechanism may aid nutrient absorption in smaller birds with shorter intestines.
- Increased paracellular uptake in smaller birds could enhance vulnerability to toxicants.
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