Structural and Elemental Quantification of Coelomate Hard Tissues for Biomaterial Applications

Abstract

Biomineralization plays a fundamental role in skeletal formation, influencing structural integrity, mechanical
function, and evolutionary adaptations across different phyla. The skeletal compositions of mollusks, chordates,
and echinoderms vary significantly due to differences in mineral content and microstructural organization. This
study aims to compare the skeletal structures of Ostreola equestris (Mollusca), Larimichthys crocea (Chordata), and
Strongylocentrotus purpuratus (Echinodermata) to understand species-specific biomineralization strategies and their
functional significance. Skeletal samples were collected from the SDC Vivarium Repository and subjected to
advanced analytical techniques. Scanning electron microscopy (SEM) was used to examine surface morphology and
microstructural organization. X-ray diffraction (XRD) identified the crystalline phases of skeletal minerals, while
energy-dispersive X-ray spectroscopy (EDAX) quantified elemental composition. These methods provided a
comprehensive assessment of mineralization patterns in the selected species. SEM analysis revealed that Ostreola
equestris exhibited a calcium carbonate-based exoskeleton with prismatic and nacreous layers. XRD confirmed
calcite as the dominant mineral, while EDAX detected high calcium and trace magnesium. Larimichthys crocea
displayed a hydroxyapatite-rich skeleton with fibrous collagen networks, with XRD confirming hydroxyapatite and
EDAX detecting calcium, phosphorus, sodium, and magnesium. Strongylocentrotus purpuratus showed an amorphous
calcite skeleton with mutable connective tissues, with XRD revealing a high amorphous fraction and EDAX
indicating low calcium levels with significant organic matrix content. The study highlights distinct biomineralization
strategies, where mollusks form rigid calcium carbonate exoskeletons, chordates balance mineralization with
collagen for flexibility, and echinoderms utilize amorphous calcite for skeletal adaptability. These findings have
implications for biomaterials science, paleontology, and evolutionary biology, offering insights into species
adaptations and bio-inspired materials development.