Twin Peaks: interrogating otolith pairs to see whether they keep their stories straight - Data Collection

To tackle the question of the reliability of otoliths as recorders of individual life events, we compared the information enclosed in otolith pairs: sagittae pair and sagitta/lapillus. We used the synchrotron XRF methodology, which enabled comparison of this information at both global and hyper-fine scales. Using otoliths of diadromous pipefish, we compared element incorporation in each pair with a focus on: (i) environmental and transition between water bodies with strontium (Sr) and heavy metals, (ii) temporal information and age estimation based on sulfur (S) incorporation (iii) otolith growth and biomineralisation processes with zinc (Zn). Results show that the global information in terms of Sr and heavy metals given by both otoliths of a pair (left and right sagittae or sagitta/lapillus) is the same and that any otolith may be used to retrieve such global data. In terms of S-based growth increment counts, the numbers are the same between two otoliths of a same kind but the sagitta - lapillus of a pair show a significant difference, the later endowed with lower features, which can be consistent with the otoliths’ developmental dyschronia. Finally, hyperfine scale analysis of element distribution reveals that the otolith has intrinsic growth mechanisms, which can lead to heterogeneous elemental incorporation. The present results lead us to address the study of the growth processes of the biomineralised otolith, a highly organised inorganic/organic structure, which has statoacoustic roles, under a fluid mosaic perspective.