Jennifer A. Flannery Lauren T. Toth Philip M. Gravinese 2016 <p>The larvae of the Florida stone crab, <i>Menippe mercenaria</i>, migrate through a variety of habitats as they develop and, therefore, experience a broad range of environmental conditions through ontogeny. Environmental variability experienced by the larvae may result in distinct elemental signatures within the exoskeletons, which could provide a tool for tracking the environmental history of larval stone crab populations. A method was developed to examine trace-element ratios, specifically magnesium-to-calcium (Mg/Ca) and strontium-to-calcium (Sr/Ca) ratios, in the exoskeletons of <i>M. mercenaria</i> larvae. Two developmental stages of stone crab larvae were analyzed—stage III and stage V. Specimens were reared in a laboratory environment under stable conditions to quantify the average ratios of Mg/Ca and Sr/Ca of larval stone crab exoskeletons and to determine if the ratios differed through ontogeny. The elemental compositions (Ca, Mg, and Sr) in samples of stage III larvae (n = 50 per sample) from 11 different broods (mean Sr/Ca = 5.916 ± 0.161 millimole per mole [mmol mol⁻¹]; mean Mg/Ca = 218.275 ± 59.957 mmol mol⁻¹) and stage V larvae (n = 10 per sample) from 12 different broods (mean Sr/Ca = 6.110 ± 0.300 mmol mol⁻¹; mean Mg/Ca = 267.081 ± 67.211 mmol mol^–1) were measured using inductively coupled plasma optical emission spectrometry (ICP–OES). The ratio of Sr/Ca significantly increased from stage III to stage V larvae, suggesting an ontogenic shift in Sr/Ca ratios between larval stages. The ratio of Mg/Ca did not change significantly between larval stages, but variability among broods was high. The method used to examine the trace-element ratios provided robust, highly reproducible estimates of Sr/Ca and Mg/Ca ratios in the larvae of <i>M. mercenaria</i>, demonstrating that ICP–OES can be used to determine the trace-element composition of chitinous organisms like the Florida stone crab.</p> application/pdf 10.3133/ofr20161148 en U.S. Geological Survey A methodology for quantifying trace elements in the exoskeletons of Florida stone crab (<i>Menippe mercenaria</i>) larvae using inductively coupled plasma optical emission spectrometry (ICP–OES) reports