A CRYSTALLOGRAPHIC STUDY OF VERTEBRATE OTOLITHS

TLDR

Otoliths occur as statoconia, microstatoliths, and statoliths; statoliths and microstatoliths are always polycrystalline, while statoconia can be polycrystalline or single crystals, and some elasmobranchs also have exogenous statoconia made of sea‑sand. The study examined crystallographic properties of otoliths from 58 vertebrate species using polarization microscopy and X‑ray diffraction. The otoliths are composed of five minerals—apatite, calcite, aragonite, vaterite, and calcium carbonate monohydrate—and the study discusses crystallographic and biological aspects that may inform vertebrate phylogeny and otolith function. 1.

Abstract

1. The crystallographic properties of otoliths from 58 vertebrate species were investigated by means of polarization microscopy and x-ray diffraction.2. The otoliths occur as statoconia, microstatoliths, and statoliths.3. While statoliths and microstatoliths always are polycrystalline, statoconia may either be polycrystalline or single crystals.4. Five different minerals, viz., apatite, calcite, aragonite, vaterite and calcium carbonate monohydrate, compose the endogenous otoliths in the vertebrate labycarbonate monohydrate, compose the endogenous otoliths in the vertebrate labyrinth. Some elasmobranchs have in addition exogenous statoconia consisting of sea-sand.5. Some crystallographic and biological aspects are discussed and it is suggested that the findings may be of some value for the study of the phylogeny of vertebrates and also may aid towards a better understanding of the function of the otolith organ.