Comparative crystallography of vertebrate otoconia

Area of Science:

• Geology
• Paleontology
• Biomineralization

Background:

• Otoconia and otoliths are calcium carbonate structures crucial for balance and hearing in vertebrates.
• The polymorph of calcium carbonate (CaCO3) in these structures can vary across different species.
• Understanding these variations provides insights into evolutionary and environmental adaptations.

Purpose of the Study:

• To investigate the CaCO3 polymorph present in otoconial material from diverse vertebrate groups.
• To compile existing data and present new findings on otoconial polymorphs, with a focus on reptiles.

Main Methods:

• Collection and analysis of otoconial and otolith samples from various vertebrate species.
• Identification of CaCO3 polymorphs (e.g., aragonite, calcite) using established crystallographic techniques.

Main Results:

• Otoconia and otoliths from bony fish, amphibians, and reptiles were predominantly found to be aragonitic.
• Otoconia and otoliths from birds and mammals were primarily identified as calcitic.
• New data, particularly for reptiles, were presented, contributing to the existing body of knowledge.

Conclusions:

• A clear correlation exists between vertebrate taxonomic groups and the CaCO3 polymorphs found in their otoconia and otoliths.
• The functional or evolutionary significance of this polymorph-taxonomic group relationship warrants further investigation.