Carapace asymmetry: A possible biomarker for metal accumulation in adult olive Ridleys marine turtles?

Highlights: • Developmental instability index can determine the asymmetry with just a carapace photo. • More asymmetric adult turtles presented higher concentrations of some of the analyzed metals. • Ridley's carapace asymmetry could be use as biomarker for some metals accumulation. - Abstract: The Olive Ridley marine turtle (Lepidochelys olivacea) is characterized by individual morphological variability in the number and shape of scutes. The influence of pollutants on developmental instability and one of its consequences, the asymmetry of individuals, has been demonstrated in several species, especially invertebrates and some birds. However, the use of this asymmetry as a biomarker of contamination in adult individuals has never been explored. We developed an index to quantify developmental instability (DIx) based on the number and relative size of costal carapace scutes. The link between DIx and inorganic elements concentrations was explored in various tissues of stranded turtles from the Southern Mexican Pacific. The relationships between adult contamination and DIx could directly or indirectly reflect (i) the disruption of metal elimination in the adult stage dependent on embryonic perturbation and thus determining DIx, (ii) the difference in metal absorption dependent on DIx status, or (iii) DIx linked to other unknown factors.