Structural characterization and regulation of the mechanical properties of the carapace cuticle in tri-spine horseshoe crab (Tachypleus tridentatus)

Horseshoe crab (order Xiphosura) has a large and thick carapace that has evolved as a protective tool to defend against predators and resist impacts from surf-zone turbulence. The naturally occurring spatial variation in the mechanical properties of the carapace cuticle need to be investigated to un...

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Bibliographic Details
Published in:Journal of the mechanical behavior of biomedical materials 2022-01, Vol.125, p.104954-104954, Article 104954
Main Authors: Ma, Yaopeng, Guo, Ce, Dai, Ning, Shen, Jingyu, Guan, Jigang
Format: Article
Language:English
Subjects:
Animal Shells
Animals
Arthropod cuticle
Biological materials
Horseshoe Crabs
Mechanical properties
Regulation mechanism
Tri-spine horseshoe crab
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Summary:Horseshoe crab (order Xiphosura) has a large and thick carapace that has evolved as a protective tool to defend against predators and resist impacts from surf-zone turbulence. The naturally occurring spatial variation in the mechanical properties of the carapace cuticle need to be investigated to understand their regulatory mechanism and the underlying design strategies. In this work, we used a combination of high-resolution optical microscopy, scanning electron microscopy, (SEM) and energy-dispersive X-ray spectroscopy (EDS) to evaluate the multiscale microstructure and elemental composition of the cuticle of tri-spine horseshoe crab (Tachypleus tridentatus). The moduli, ultimate strengths, and failure strains of the three individual layers and the entire cuticle were systematically characterized in both the dry and hydrated states. The failure behaviors and energy absorption of the cuticle involved stress stiffening, toughness mechanism and environmental adaptation were analyzed qualitatively and quantitatively and then correlated with the morphological features in different cuticle regions. The mechanical properties are primarily influenced by the endocuticle thickness ratio; a higher thickness ratio corresponds to more stacking of the vertical lamellae, leading to a lower modulus, weaker strength, and greater elongation of the endocuticle. Radial energy is absorbed primarily by the endocuticle, with the energy absorbed in the radial direction being nearly twice that absorbed in the circumferential direction. This is attributed to the larger failure strain and relatively small decrease in the stress plateau in the radial direction. The findings provide a deeper understanding of how nature modulates the cuticle's mechanical properties and inspiration for developing high-performance synthetic composites. [Display omitted] •Spatial gradients in mechanical properties of carapace cuticle were revealed.•The relationships between structural parameters and mechanical properties were studied systematically.•Energy absorption capacity of epicuticle, exocuticle and endocuticle were tested in circumferential and radial direction.
ISSN:1751-6161
1878-0180
DOI:10.1016/j.jmbbm.2021.104954