Hummingbirds arrest their kidneys at night: diel variation in glomerular filtration rate in Selasphorus platycercus
Date
2004
Authors
Hartman Bakken, B.
McWhorter, T.
Tsahar, E.
Martinez del Rio, C.
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Journal article
Citation
Journal of Experimental Biology, 2004; 207(25):4383-4391
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Bradley Hartman Bakken, Todd J. McWhorter, Ella Tsahar and Carlos Martínez del Rio
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Abstract
Small nectarivorous vertebrates face a quandary. When feeding, they must eliminate prodigious quantities of water; however, when they are not feeding, they are susceptible to dehydration. We examined the role of the kidney in the resolution of this osmoregulatory dilemma. Broad-tailed hummingbirds (Selasphorus platycercus) displayed diurnal variation in glomerular filtration rate (GFR). During the morning, midday and evening, GFRs were 0.9±0.6, 1.8±0.4 and 2.3±0.5 ml h–1, respectively. At midday, GFR increased linearly with increased water intake. During the evening, hummingbirds decreased renal fractional water reabsorption linearly with increased water intake. Broad-tailed hummingbirds appeared to cease GFR at night (–0.1±0.2 ml h–1) and decreased GFR in response to short-term (~1.5 h) water deprivation. GFR seems to be very responsive to water deprivation in hummingbirds. Although hummingbirds and other nectarivorous birds can consume astounding amounts of water, a phylogenetically explicit allometric analysis revealed that their diurnal GFRs are not different from the expectation based on body mass.
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© The Company of Biologists Ltd 2004