| Research Abstract |
1) Ear crystals (otoconia) were taken out from 421 individuals of 11 orders, 24 families and 54 species in elasmobranchs and 4 individuals of Chimaera phantasma in Holocephali, collected mainly from Suruga Bay, central Japan.
2) Ca, P, Mg, Sr, and Ba contents of the otoconia of 103 individuals of 46 species were measured by microelement analysis with inductively coupled plasma mass spectrometry (ICPMS), and it carried out chemical analysis on the sample surface on a part of specimens with an energy-dispersible X-ray diffractometer (EDX).
3) Otoconia of many species showed white, though in sawfish, angel shark, bullhead shark and 3 species of electric rays, it included many black particles.
4) Weight of otoconia ranged mainly from 0.01 to 0.5 g, though large specimen of silky shark and heavy otoconia of 6.43 g. It was different in species and fish size, and became heavy with fish growth
5) Elementary content to 1 g of otoconia in many species without black particles was 192-359 mg in Ca, be
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low 5 mg in Mg, 4-6.3 mg in Sr, and below 17μg in Ba. Molar fraction of each element was over 0.93 in Ca, 0.001-0.009 in Mg, 0.016-0.019 in Sr, and below 0.00002 in Ba. On the other hand, that in species kept black particles was below 32 mg in Ca, 2.09-4.96 mg in Mg, below 0.23 mg in Sr, and below 50.71μg in Ba. Molar fraction in the latter species was much different from the former species.
6) EDX detected Fe and Ti in the black particles. Otocconia with black particles contained silicate and iron sulfide.
7) Ca:P ratio in otoconia of swell shark, star-spotted smooth dogfish, tope shark, smooth hammerhead, red stingray, pitted stingray tended to decrease with growth.
8) Cluster analysis of the similarity in each species based on the ratio of 4 elements to Ca divided 6 species with black particles from the rest, and angel shark and bullhead shark were isolated within 6 species. Among the rest 40 species, spinner shark severed oneself. The remains were cut into 5 separate groups.
9) Species composition of each group was mainly reflected in the phylogeny of elasmobranchs, though it suggested to relate with their food habits and habitat.
10) The reason that the otoconia of 6 species contained Fe and Ti wag unknown. Therefore, their origin, chemical constitutional formula and biological role will need to be made clear. Less
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