Composite material in the sea urchin Cidaris rugosa: Ordered and disordered micrometre-scale bicontinuous geometries

Date

2024

Authors

Jessop, Anna-Lee
Millsteed, Allan J.
Kirkensgaard, Jacob Judas Kain
Shaw, Jeremy
Clode, Peta L.
Schroeder-Turk, Gerd

Journal Title

Journal ISSN

Volume Title

Publisher

Royal Society Publishing

Abstract

The sponge-like biomineralized calcite materials found in echinoderm skeletons are of interest in terms of both structure formation and biological function. Despite their crystalline atomic structure, they exhibit curved interfaces that have been related to known triply periodic minimal surfaces. Here, we investigate the endoskeleton of the sea urchin Cidaris rugosa that has long been known to form a microstructure related to the Primitive surface. Using X-ray tomography, we find that the endoskeleton is organized as a composite material consisting of domains of bicontinuous microstructures with different structural properties. We describe, for the first time, the co-occurrence of ordered single Primitive and single Diamond structures and of a disordered structure within a single skeletal plate. We show that these structures can be distinguished by structural properties including solid volume fraction, trabeculae width and, to a lesser extent, interface area and mean curvature. In doing so, we present a robust method that extracts interface areas and curvature integrals from voxelized datasets using the Steiner polynomial for parallel body volumes. We discuss these very large-scale bicontinuous structures in the context of their function, formation and evolution.

Description

Keywords

calcite, biomineralization, diamond, calciumcarbonate, curvature

Citation

Source

Journal of the Royal Society Interface

Type

Journal article

Book Title

Entity type

Access Statement

Open Access

License Rights

Creative Commons Attribution License

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