From doubly labelled water to half-life; validating radio-isotopic rubidium turnover to measure metabolism in small vertebrates

Author(s)

Tomlinson, Sean ^[1] ; Maloney, Shane K. ^[2] ; Withers, Philip C. ^[1] ; Voigt, Christian C. ^[3] ; Cruz-Neto, Ariovaldo P. ^[4]

Affiliation

^[1] Univ Western Australia, Fac Sci, Sch Anim Biol, Crawley, WA 6009 - Australia

^[2] Univ Western Australia, Sch Anat Physiol & Human Biol, Fac Sci, Crawley, WA 6009 - Australia

^[3] Leibniz Inst Zoo & Wildlife Res, Berlin - Germany

^[4] Univ Estadual Paulista, Dept Zool, Rio Claro, SP - Brazil

• Document type: Journal article
• Source: METHODS IN ECOLOGY AND EVOLUTION; v. 4, n. 7, p. 619-628, JUL 2013.
• Web of Science Citations: 8

Abstract

1. The doubly labelled water method (DLW) is widely used to measure field metabolic rate (FMR), but it has some limitations. Here, we validate an innovative technique for measuring FMR by comparing the turnover of isotopic rubidium (Rb-86 k(b)) with DLW depletion and the rate of CO2 production ((V) over dot(co2)) measured by flow-through respirometry (FTR) for two dunnart species (Marsupialia: Dasyuridae), Sminthopsis macroura (17g) and Sminthopsis ooldea (10g). 2. The rate of metabolism as assessed by (V) over dot(co2) (FTR) and Rb-86 k(b) was significantly correlated for both species (S.macroura, r(2)=081, P=119x10(-5); S.ooldea, r(2)=063, P=384x10(-4)), as was (V) over dot(co2) from FTR and DLW for S.macroura (r(2)=043, P=0039), but not for S.ooldea (r(2)=029, P=0168). There was no relationship between (V) over dot(co2) from DLW and Rb-86 k(b) for either species (S.macroura r(2)=022, P=0169; S.ooldea r(2)=021, P=0253). We conclude that Rb-86 k(b) provided useful estimates of metabolic rate for dunnarts. 3. Meta-analysis provided different linear relationships between (V) over dot(co2) and Rb-86 k(b) for endotherms and ectotherms, suggesting different proportionalities between metabolic rate and Rb-86 k(b) for different taxa. Understanding the mechanistic basis for this correlation might provide useful insights into the cause of these taxonomic differences in the proportionality. At present, it is essential that the relationship between metabolic rate and Rb-86 k(b) be validated for each taxon of interest. 4. The advantages of the Rb-86 technique over DLW include lower equipment requirements and technical expertise, and the longer time span over which measurements can be made. The Rb-86 method might be particularly useful for estimating FMR of groups for which the assumptions of the DLW technique are compromised (e.g. amphibians, diving species and fossorial species), and groups that are practically challenging for DLW studies (e.g. insects). (AU)

• FAPESP's process: 08/57687-0 - Effects of global climate change of the Brazilian fauna: a conservation physiology approach
• Grantee: Carlos Arturo Navas Iannini
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants