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Validation of Body Condition Indices and Quantitative Magnetic Resonance in Estimating Body Composition in a Small Lizard
Author(s) -
Warner Daniel A.,
Johnson Maria S.,
Nagy Tim R.
Publication year - 2016
Publication title -
journal of experimental zoology part a: ecological genetics and physiology
Language(s) - English
Resource type - Journals
eISSN - 1932-5231
pISSN - 1932-5223
DOI - 10.1002/jez.2053
Subject(s) - lean body mass , anolis , lizard , biology , linear regression , body water , regression , regression analysis , fat mass , body mass index , physiological condition , body weight , statistics , mathematics , zoology , ecology , endocrinology
Measurements of body condition are typically used to assess an individual's quality, health, or energetic state. Most indices of body condition are based on linear relationships between body length and mass. Although these indices are simple to obtain, nonlethal, and useful indications of energetic state, their accuracy at predicting constituents of body condition (e.g., fat and lean mass) are often unknown. The objectives of this research were to (1) validate the accuracy of another simple and noninvasive method, quantitative magnetic resonance (QMR), at estimating body composition in a small‐bodied lizard, Anolis sagrei , and (2) evaluate the accuracy of two indices of body condition (based on length–mass relationships) at predicting body fat, lean, and water mass. Comparisons of results from QMR scans to those from chemical carcass analysis reveal that QMR measures body fat, lean, and water mass with excellent accuracy in male and female lizards. With minor calibration from regression equations, QMR will be a reliable method of estimating body composition of A. sagrei . Body condition indices were positively related to absolute estimates of each constituent of body composition, but these relationships showed considerable variation around regression lines. In addition, condition indices did not predict fat, lean, or water mass when adjusted for body mass. Thus, our results emphasize the need for caution when interpreting body condition based upon linear measurements of animals. Overall, QMR provides an alternative noninvasive method for accurately measuring fat, lean, and water mass in these small‐bodied animals.

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