Body wall structure in the starfish Asterias rubens

Area of Science:

• Marine Biology
• Biomechanics
• Materials Science

Background:

• Starfish body walls comprise magnesium calcite ossicles linked by collagenous tissue and muscles.
• Remarkable stiffness variability is attributed to the collagenous component's mechanical mutability.

Purpose of the Study:

• To investigate the structure and organization of the starfish body wall in Asterias rubens.
• To gain new insights into the anatomical basis of mechanical properties in echinoderm tissues.

Main Methods:

• Trichrome staining for muscular and collagenous components.
• X-ray microtomography for 3D visualization of the calcareous endoskeleton.
• Scanning synchrotron small-angle X-ray diffraction (SAXD) for fibrillar analysis of collagenous tissue.

Main Results:

• Detailed structure of interossicular muscles and collagenous tissue with loop-shaped straps.
• 3D architecture of ossicles and their interactions revealed.
• Variable collagen fibril alignment in aboral body wall and uniform low orientation in ambulacrum.
• Distinct collagen fibril D-period lengths and higher overlap/D-period ratios compared to mammals.

Conclusions:

• The study provides novel insights into the starfish body wall's anatomy and collagenous tissue structure.
• Findings lay the groundwork for understanding the mechanical properties of echinoderm body wall composites.
• Anatomical organization suggests body shape changes are achieved via muscle action.