Scanning electron microscopic study of amphibians otoconia

The otoconia of three adult amphibian species were studied by scanning electron microscopy (SEM). Two calcium carbonate polymorphs (calcite and aragonite) were shown to be present at specific sites in the membranous labyrinth. The utricle contained only calcitic otoconia, whereas the saccule, lagena and endolymphatic sac contained only aragonitic otoconia. SEM examination demonstrated that there is a morphological difference in otoconia according to the site of origin in the membranous labyrinth, and that a mechanism for determining the range of otoconial sizes according to this difference in otoconial morphology may exist.