Mechanical properties, degree of sclerotisation and elemental composition of the gastric mill in the red swamp crayfish Procambarus clarkii (Decapoda, Crustacea)

Abstract The gastric mill of Decapoda is a unique feature consisting of interacting teeth, stabilizing ossicles, and particle sorting setae. As this organ is involved in the mechanical fragmentation of the food, it serves as interface between organism and environment. There is an ongoing debate to which extend structures are shaped due to phylogeny or to ecology. As material properties complement morphology and hold information about functionality and trophic preferences, we here aim at providing a basis for more intensely comparative research on material composition and properties of gastric mill components. Data on the micro-structure, documented via scanning electron microscopy (SEM), on the elemental composition, determined by energy-dispersive X-ray spectroscopy (EDX, EDS), on the heterogeneities in material properties, visualized by confocal laser scanning microscopy (CLSM), and on the mechanical properties hardness and elasticity (i.e., Young’s modulus), tested by nanoindentation technique, of gastric mill components from the red swamp crayfish Procambarus clarkia is here presented. The elemental composition of gastric mill components was studied previously in other taxa, but the mechanical properties were never tested before. As epicuticle and exocuticle could be analyzed individually, due to rather large thickness of the epicuticle, material property gradients, with values decreasing from the interacting surface towards interior, could be determined. Finally, we were able to relate the mechanical property data and the autofluorescence signals with the elemental composition and the degree of tanning.