Polymorphic crystalline structure of fish otoliths

Although most otoliths of teleost fishes contain aragonite, a detailed survey of the otoliths of serveral species confirms that other crystalline forms of calcium carbonate occur. Otoliths of Hoplostethus atlanticus, Pagrus major, Macruronus novaezelandiae, Merluccius australis, Congiopodus coriaceus, Kathetostoma giganteum, Argentina elongata, Rhomobosolea tapirina, Neophrynichthys latus, Coelorinchus aspercephalus, Paranothothenia microlepidota, and Gonorhynchus gonorhynchus contained the aragonite, calcite, and vaterite morphs of calcium carbonate in varying proportions. Aragonitic otoliths of Allocyttus niger, Hoplostethus altlanticus, and Pagrus major contained sequences of calcite-like crystals. The surface of the vateritic otolith of Acipenser brevirostrum is shown in detail. Three classes of information are stored in the crystalline structure of the otolith: shape conservation, coexisting crystal morphs, and consecutive changes in crystal morph. Analysis of this crystalline information supports the hypothesis of control of growth of the otolith by proteins from the sensory epithelium or macula. Protein variation involved may be genetic in origin, or non-genetic arising from "stuttering" of the translation process. Proteins extracted from vateric and aragonitic morphs of the otolith of Macruronus novaezelandiae showed differences in infared absorption spectra that were consistent with two different amino acid sequences. © 1993 Wiley-Liss, Inc.