Cuticle on the jaws of the jewel beetle larva is equivalent in hardness and stiffness to stainless steel through structural and biochemical pathways.
"The arthropod cuticle is a remarkable and versatile biological material commonly composed of chitin and proteins. Lessons can be learned from the way it is adapted to fit its functions. The larval jewel beetle, Pseudotaenia frenchi, demonstrates hardness in the cutting edge of the mandibles in excess of the mineralized carapace of stone crabs and compares favourably with some stainless steels. Yet this is a form of cuticle which is devoid of transition metals or mineralization. In seeming contradiction, the similarly dark coloured adult beetle mandibles contain the transition metal manganese, but are significantly softer. Energy dispersive X-ray analysis and infrared spectroscopy have been used to investigate the differences in composition of mandible cuticle of the adult and larval beetles…This study raises questions regarding the current understanding of the function of transition metals in cuticle. It also demonstrates that chitin-based biological materials devoid of biomineralization or metal incorporation can achieve better performance than previously documented." (Cribb et al. 2010:3152)
"The larval mandibular cuticle, measured either wet or dry, is harder than many other biological materials noted for their mechanical properties, including the mineralized stone crab carapace. It is also equivalent to the maximal hardness measured for a range of stainless steels. This larval material holds out promise that by analysing its hierarchical structure and chemistry further we can determine how such a biopolymer can reach previously unrecognized levels of performance." (Cribb et al. 2010:3156)
Learn more about this functional adaptation.
- Cribb B W; Lin C -L; Rintoul L; Rasch R; Hasenpusch J; Huang H. 2010. Hardness in arthropod exoskeletons in the absence of transition metals. Acta Biomaterialia. 6: 3152–3156.
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