Differences in the concentrations of trace elements among different hard structures and their potential application in species identification: a case study on Loliginidae cryptic species

Abstract

ABSTRACT It is a challenge to identify Uroteuthis chinensis and Uroteuthis edulis, which widely distributed in the coast of China, due to their morphological similarity. Trace elements in cephalopod hard structures may indicate species difference. In this study, with the laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS), we analysed trace elements in three kinds of hard structures (statolith, beak and eye lens), determined the differences in the concentrations of trace elements among different hard structures and identified U. chinensis and U. edulis caught from northern South China Sea with the determined elemental signatures in different ontogenetic stages. Nine elements were detected from the squid's statolith and beak, eight elements were detected from eye lens. Calcium (Ca) was the most abundant element in both statolith and beak, whereas phosphorus (P) was the most abundant element in eye lens. The significant differences in some trace elements were determined among different ontogenetic stages in both species. Discriminant analysis results showed that the correct classification rate based on trace elements in the late life stages (sub-adult and adult) was higher than that based on trace elements in the early life stages (embryonic, paralarval and juvenile). All three hard structures yielded a similar classification rate.