The armored carapace of the boxfish

Wen Yang; Steven E Naleway; Michael M Porter; Marc A Meyers; Joanna McKittrick

doi:10.1016/j.actbio.2015.05.024

The armored carapace of the boxfish

Acta Biomater. 2015 Sep:23:1-10. doi: 10.1016/j.actbio.2015.05.024. Epub 2015 May 28.

Authors

Wen Yang¹, Steven E Naleway², Michael M Porter¹, Marc A Meyers³, Joanna McKittrick⁴

Affiliations

¹ Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093-0411, USA.
² Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093-0411, USA. Electronic address: snaleway@eng.ucsd.edu.
³ Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093-0411, USA; Dept. of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093-0411, USA; Dept. of Nanoengineering, University of California, San Diego, La Jolla, CA 92093-0411, USA.
⁴ Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093-0411, USA; Dept. of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093-0411, USA.

PMID: 26026303
DOI: 10.1016/j.actbio.2015.05.024

Abstract

The boxfish (Lactoria cornuta) has a carapace consisting of dermal scutes with a highly mineralized surface plate and a compliant collagen base. This carapace must provide effective protection against predators as it comes at the high cost of reduced mobility and speed. The mineralized hydroxyapatite plates, predominantly hexagonal in shape, are reinforced with raised struts that extend from the center toward the edges of each scute. Below the mineralized plates are non-mineralized collagen fibers arranged in through-the-thickness layers of ladder-like formations. At the interfaces between scutes, the mineralized plates form suture-like teeth structures below which the collagen fibers bridge the gap between neighboring scutes. These sutures are unlike most others as they have no bridging Sharpey's fibers and appear to add little mechanical strength to the overall carapace. It is proposed that the sutured interface either allows for accommodation of the changing pressures of the boxfish's ocean habitat or growth, which occurs without molting or shedding. In both tension and punch testing the mineralized sutures remain relatively intact while most failures occur within the collagen fibers, allowing for the individual scutes to maintain their integrity. This complex structure allows for elevated strength of the carapace through an increase in the stressed area when attacked by predators in both penetrating and crushing modes.

Keywords: Bioinspired; Boxfish; Carapace; Fracture mechanism; Scute.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animal Shells / diagnostic imaging
Animal Shells / physiology*
Animal Shells / ultrastructure*
Animals
Compressive Strength / physiology*
Elastic Modulus / physiology
Hardness / physiology
Radiography
Stress, Mechanical
Tensile Strength / physiology
Tetraodontiformes / anatomy & histology*
Tetraodontiformes / physiology*
Weight-Bearing / physiology*