A Spider's Fang: How to Design an Injection Needle Using Chitin‐Based Composite Material

Abstract

Spiders mainly feed on insects. This means that their fangs, which are used to inject venom into the prey, have to puncture the insect cuticle that is essentially made of the same material, a chitin‐protein composite, as the fangs themselves. Here a series of structural modifications in the fangs of the wandering spider Cupiennius salei are reported, including texture variation in chitin orientation and arrangement, gradients in protein composition, and selective incorporation of metal ions (Zn and Ca) and halogens (Cl). These modifications influence the mechanical properties of the fang in a graded manner from tip to base, allowing it to perform as a multi‐use injection needle that can break through insect cuticle, which is made of a chitin composite as well.

Feeding in billfishes: inferring the role of the rostrum from a biomechanical standpoint

“…Billfish rostra are subject to periodic loadings over long periods of time, which may result in fatigue damage and favor the formation of microcracks in this stiffer area, as in bone and nacre (Currey, 1984). Similar gradients of stiffness have been reported in other biological structures including bird feathers (Macleod, 1980;Bonser and Purslow, 1995), squid beaks (Miserez et al, 2008) and spider fangs (Politi et al, 2012); the latter two systems also acting as predatory weapons, similar to billfish rostra. In addition, the higher incidence of remodeled bone morphology in the distal region of the rostrum suggest that the tissue is under regular loading and therefore more prone to damage and consequently, remodeling (Atkins et al, 2014).…”

Mechanics of metal-catecholate complexes: The roles of coordination state and metal types

“…Measurements of the mechanical properties after removing metals from the cuticle showed 2-fold decrease in the hardness, suggesting a significant impact of the coordination complex on the material properties3. In the fangs of the wandering spider Cupiennius salei , Zn-His coordination complexes were also found in the matrix of chitin and Zn-containing proteins2. Connection was then identified between the mechanical properties and Zn/Cl enrichment in this fiber-reinforced biocomposite.…”

“…Many biological materials with outstanding mechanical, adhesive and frictional properties benefit from their hierarchical composite structures, within which the reinforcing role of metal complexation in the polymer network phase was recently highlighted12. For example, it was reported that the Fe-catecholate (1,2-dihydroxybezene) complexes in mussel byssus cuticles provide effective crosslinking strategies between metal ions and catecholic amino acid dopa (3,4-dihydroxypheylalanine) in mussel foot protein 1 (mfp-1) chains13.…”

“…Connection was then identified between the mechanical properties and Zn/Cl enrichment in this fiber-reinforced biocomposite. Moreover, the inhomogeneous metal distribution in the fang might have additional implications in its graded mechanical properties, with an over two-fold increase in hardness and 1.5-fold increase in stiffness measured from the base to the tip2.…”

Poriferan Chitin as a Versatile Template for Extreme Biomimetics

“…Chitin plays a major role in biological structural materials with significant physical attributes, such as lobster shells [44], the mineralized dactyl club of the stomatopods [97,112], diatoms cell [20], glass sponges [52], copepod teeth's [115], spider fangs [116] and nacre [117]. Surprisingly, the industrial uses of chitinous materials have been largely based on its chemical characteristics (e.g., high nitrogen content) and unique biological properties, rather than on its ability to form structural composites with novel mechanical properties [117].…”