Nuclear Microprobe Mapping of Statoliths of Chokka Squid Loligo vulgaris reynaudii d'Orbigny, 1845.

Loliginid squid statoliths were broken in half and their elemental composition was assessed using the nuclear microprobe technique. Proton induced X-ray emission and proton backscattering were used simultaneously. True, quantitative maps of calcium and strontium distribution in the frontal plane were obtained using a rapid-matrix-transform method called Dynamic Analysis. These measurements were complemented by observations with scanning electron microscopy and light microscopy. In juvenile and adult statoliths, Sr was concentrated in the wing and adjacent areas, whereas the Ca concentration was highest on the edge of the lateral dome. In contrast, Sr and Ca were uniformly distributed in the statoliths of paralarval squid. Increments showed best definition in the areas anterior and adjacent to the wing, corresponding to areas of high Sr content. Although temperature, sex, maturity, and the administration of oxytetracycline may influence the quantitative distribution of Ca and Sr in the statoliths of adult squid, they do not appear to affect the general pattern described above. The finding that Sr is concentrated in regions adjacent to the macula where the clearest increments are found in loliginid statoliths supports the hypothesis linking strontium with the regulation of statolith deposition and the definition of daily increments.