Structural design of the echinoid's trabecular system

Area of Science:

• Marine Biology
• Biomechanics
• Paleontology

Background:

• Echinoid skeletons (stereom) are lightweight, micro-beam frameworks.
• The 2D design of stereom is known, but its 3D spatial architecture is not well understood.
• Understanding spatial architecture is crucial for interpreting its load-bearing principles.

Purpose of the Study:

• To analyze the spatial architecture of the echinoid trabecular system.
• To investigate the structural principles of this load-bearing construction.

Main Methods:

• Analysis of the echinoid's trabecular system using eight topological descriptors.
• Division of echinoid plates into central (unordered stereom) and marginal (ordered stereom) regions.

Main Results:

• Basal topology of both plate regions is similar.
• The trabecular system features short, stocky, and minimally tortuous trabeculae.
• Majority of trabeculae form 3N configurations (three trabeculae meeting at a node) with ~120° angles, creating planar, triangular motifs.
• Trabeculae exhibit a 60° orientation perpendicular to the plate surface and directional orientation in the horizontal plane.
• These orientations effectively resist multi-dimensional loads and distribute stress across the skeleton.

Conclusions:

• The spatial architecture of the echinoid trabecular system is a performative, lightweight, and load-bearing system.
• The structural design efficiently manages applied loads, highlighting evolutionary adaptations for skeletal integrity.