Crystallographic and chemical composition of otoconia in the salamander Pleurodeles waltl

Abstract

The aim of the present study was to define the morphology and the crystallographic and chemical composition of otoconia in different regions of the inner ear in Pleurodeles waltl (urodele amphibian). The inner ear of adults was microdissected and otoconia were analyzed by scanning electron microscopy (SEM), X-ray diffraction, energy dispersive X-ray (EDX) and transmission electron microscopy. Two types of crystals were detected by SEM. Otoconia had different shapes depending on their location in the membranous labyrinth. One type had a cylindrical body with a triplanar smooth facet at each end, the other ones had either a prismatic shape with flat sides and end faces or a fusiform shape with rounded body and pointed end. The forms corresponded to those previously identified by other authors. These two types of otoconia had different X-ray diffraction patterns. The cylindrical otoconia were calcitic and located in the utricle, the other ones were aragonitic and located in the saccule, lagena and endolymphatic sac. An analysis by EDX indicated that both types of otoconia contained about 95% calcium with trace quantities of sodium, magnesium, phosphorus, sulfur, chlorine and potassium. Trace amounts of strontium was only found in the aragonitic otoconia. ß 1999 Elsevier Science B.V. All rights reserved.

Morphology and evolutionary significance of phosphatic otoliths within the inner ears of cartilaginous fishes (Chondrichthyes)

“…Phylogeny was composited from overall vertebrate data [51], acanthodian distribution [52], basal actinopterygians [53] and sarcopterygians [54] and extant chondrichthyan data [55, 56]. Otolith morphology and composition for the other major vertebrate groups was taken from literature: Acanthodii [13, 44, 45, 47], Agnatha [8, 27, 48], Osteichthyes [8, 40, 41, 43, 57, 58]…”

“…Chemical composition of the otoconia and otoliths has been uniformly reported to consist of four calcium carbonate polymorphs (calcite, vaterite, aragonite or calcium carbonate monohydrate) in extant gnathostomes [40–43]. In acanthodians, the otoliths consist of calcite [13, 44–47].…”

Influence of Silicate Anions on the Morphology of Calcite Crystals

“…Biomineralization is one such important process in which the inorganic phase of a hard tissue is formed through a template-assisted process . Microorganisms tailor-make such hard materials (with the help of bioorganic macromolecules, such as proteins, polysaccharides, or glycoproteins) and use them for structural support, gravity sensors, and protection. The chemistry and structural complexity of biominerals was reviewed in the past by Mann 7a and Ozin 7b.…”