title: Special K: testing the potassium link between radioactive rubidium (86Rb) turnover and metabolic rate.
abstract: The measurement of (86)Rb turnover recently has been suggested as a useful method for measuring field metabolic rate in small animals. We investigated a proposed mechanism of (86)Rb turnover, its analogy to K(+), by comparing the turnover of (86)Rb in a model insect, the rhinoceros beetle Xylotrupes gideon, fed a diet of plum jam or plum jam enriched with K(+) or Rb(+). The turnover of (86)Rb in the beetles on the K(+) and the Rb(+) diets was higher than that for beetles on the jam diet (F2,311=32.4; P=1.58×10(-13)). We also exposed the beetles to different ambient temperatures to induce differences in metabolic rate ( ) while feeding them the jam and K(+) diets. was higher at higher ambient temperature (Ta) for both jam (F1,11=14.56; P=0.003) and K(+) (F1,8=15.39; P=0.004) dietary groups, and the turnover of (86)Rb was higher at higher Ta for both jam (F1,11=10.80; P=0.007) and K(+) (F1,8=12.34; P=0.008) dietary groups. There was a significant relationship between (86)Rb turnover and for both the jam (F1,11=35.00; P=1.0×10(-3)) and the K(+) (F1,8=64.33; P=4.3×10(-5)) diets, but the relationship differed between the diets (F1,19=14.07; P=0.001), with a higher (86)Rb turnover in beetles on the K(+)-enriched than on the jam diet at all Ta. We conclude that (86)Rb turnover is related to K(+) metabolism, and that this is the mechanism of the relationship between (86)Rb turnover and . Studies relating (86)Rb turnover to should maintain dietary [K] as close as possible to that of natural diets for the most accurate calibrations for free-ranging animals.
authors.affiliation: School of Animal Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Sean
authors.initials: S
authors.lastname: Tomlinson
authors.forename: Priya D
authors.initials: PD
authors.lastname: Mathialagan
authors.forename: Shane K
authors.initials: SK
authors.lastname: Maloney
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000378:metabolism*; D004734:Energy Metabolism; D005260:Female; D008297:Male; D011188:Potassium / Q000378:metabolism*; D017419:Potassium, Dietary / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism; D012414:Rubidium Radioisotopes / Q000378:metabolism*; D013696:Temperature
chemical_list: D017419:Potassium, Dietary; D012414:Rubidium Radioisotopes; D012413:Rubidium; D011188:Potassium
keywords: 86Rb kb; Insect; Isotope turnover; Metabolic rate; Xylotrupes gideon