TY - JOUR

T1 - Composite material in the sea urchin Cidaris rugosa

T2 - Ordered and disordered micrometre-scale bicontinuous geometries

AU - Jessop, Anna Lee

AU - Millsteed, Allan J.

AU - Kirkensgaard, Jacob J.K.

AU - Shaw, Jeremy

AU - Clode, Peta L.

AU - Schröder-Turk, Gerd E.

N1 - Publisher Copyright: © 2024 The Authors.

PY - 2024

Y1 - 2024

N2 - 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.

AB - 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.

KW - biomineralization

KW - calcite

KW - calcium carbonate

KW - curvature

KW - diamond

U2 - 10.1098/rsif.2023.0597

DO - 10.1098/rsif.2023.0597

M3 - Journal article

C2 - 38471532

AN - SCOPUS:85187707597

VL - 21

JO - Journal of the Royal Society Interface

JF - Journal of the Royal Society Interface

SN - 2042-8898

IS - 212

M1 - 20230597

ER -