NEXAFS imaging to characterize the physio-chemical composition of cuticle from African Flower Scarab Eudicella gralli

Abstract

The outermost surface of insect cuticle is a high-performance interface that provides wear protection, hydration, camouflage and sensing. The complex and inhomogeneous structure of insect cuticle imposes stringent requirements on approaches to elucidate its molecular structure and surface chemistry. Therefore, a molecular understanding and possible mimicry of the surface of insect cuticle has been a challenge. Conventional optical and electron microscopies as well as biochemical techniques provide information about morphology and chemistry but lack surface specificity. We here show that a near edge X-ray absorption fine structure microscope at the National Synchrotron Light Source can probe the surface chemistry of the curved and inhomogeneous cuticle of the African flower scarab. The analysis shows the distribution of organic and inorganic surface species while also hinting at the presence of aragonite at the dorsal protrusion region of the Eudicella gralli head, in line with its biological function.

Surface analysis tools for characterizing biological materials

“…Recently, this NEXAFS microscope was used to the characterize the surface chemistry across the cuticle of an African flower scarab (E. gralli). 31 Both a photograph of the head and NEXAFS carbon K-edge image of scarab head are presented in Fig. 7.…”

Resonant soft X‐ray scattering in polymer science

“…There are a few different ways of measuring in effective microscopies. One can image the electrons ejected from a sample, 33–35 or use full field microscopy 36 but for soft X‐rays of organic materials, detector and optical technology as well as the materials' nonconductive properties has made STXM the most common way to image nanoscale soft matter structure. It is in many ways a complementary tool to RSoXS, using the same photon interactions but providing a real space image.…”

Mandible elemental composition and mechanical properties from distinct castes of the leafcutter ant Atta laevigata (Attini; Formicidae)

“…These metals were identified as cross-links as they bind strongly to the biopolymers and increase the cross-linking density [35,[37][38][39][40][41]. Additionally, there are indications for the involvement of biomineralization in the insect cuticle with alkaline earth metals such as calcium (Ca) and magnesium (Mg) [34,[42][43][44][45][46]. In previous studies on ants (also in leafcutter ants), Zn was detected in the cuticle of the mandible cutting edge [5,[47][48][49][50].…”