Assessment of the amount of body water in the Red Knot (Calidris canutus): an evaluation of the principle of isotope dilution with 2H, (17)O, and (18)O as measured with laser spectrometry and isotope ratio mass spectrometry.
We have used the isotope dilution technique to study changes in the body composition of a migratory shorebird species (Red Knot, Calidris canutus) through an assessment of the amount of body water in it. Birds were quantitatively injected with a dose of water with elevated concentrations of 2H, (17)O, and (18)O. Thereafter, blood samples were taken and distilled. The resulting water samples were analysed using an isotope ratio mass spectrometry (for 2H and (18)O only) and a stable isotope ratio infrared laser spectrometry (2H, (17)O, and (18)O) to yield estimates of the amount of body water in the birds, which in turn could be correlated to the amount of body fat. Here, we validate laser spectrometry against mass spectrometry and show that all three isotopes may be used for body water determinations. This opens the way to the extension of the doubly labelled water method, used for the determination of energy expenditure, to a triply labelled water method, incorporating an evaporative water loss correction on a subject-by-subject basis or, alternatively, the reduction of the analytical errors by statistically combining the (17)O and (18)O measurements.
Kerstel
Erik R T
ER
Department of Physics, Rijksuniversiteit Groningen, Center for Isotope Research, Nijenborgh 4, 9747 AG Groningen, The Netherlands. e.r.t.kerstel@rug.nl
Piersma
Theunis
T
Piersma
Theunis A J
TA
Gessaman
James A
JA
Gessaman
G Jim
GJ
Dekinga
Anne
A
Meijer
Harro A J
HA
Visser
G Henk
GH
D000818:Animals; D001717:Birds; D001823:Body Composition; D001834:Body Water / Q000378:metabolism*; D003903:Deuterium / Q000032:analysis / Q000378:metabolism; D013058:Mass Spectrometry; D010103:Oxygen Isotopes / Q000032:analysis / Q000378:metabolism; D015203:Reproducibility of Results; D013055:Spectrophotometry, Infrared
D010103:Oxygen Isotopes; D003903:Deuterium