Hummingbirds rely on both paracellular and carrier-mediated intestinal glucose absorption to fuel high metabolism
Date
2006
Authors
McWhorter, T.
Hartman Bakken, B.
Karasov, W.
Martinez del Rio, C.
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Advisors
Journal Title
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Volume Title
Type:
Journal article
Citation
Biology Letters, 2006; 2(1):131-134
Statement of Responsibility
Todd J McWhorter, Bradley Hartman Bakken, William H Karasov and Carlos Martínez del Rio
Conference Name
Abstract
Twenty years ago, the highest active glucose transport rate and lowest passive glucose permeability in vertebrates were reported in Rufous and Anna's hummingbirds (Selasphorus rufus, Calypte anna). These first measurements of intestinal nutrient absorption in nectarivores provided an unprecedented physiological foundation for understanding their foraging ecology. They showed that physiological processes are determinants of feeding behaviour. The conclusion that active, mediated transport accounts for essentially all glucose absorption in hummingbirds influenced two decades of subsequent research on the digestive physiology and nutritional ecology of nectarivores. Here, we report new findings demonstrating that the passive permeability of hummingbird intestines to glucose is much higher than previously reported, suggesting that not all sugar uptake is mediated. Even while possessing the highest active glucose transport rates measured in vertebrates, hummingbirds must rely partially on passive non-mediated intestinal nutrient absorption to meet their high mass-specific metabolic demands.