Multimodal morphological characterization of the femoro-tibial joint of the black vine weevil (Otiorhynchus sulcatus).

As open systems, arthropod joints and mechanical articulations face common challenges such as contamination and loss of lubricant. Recent studies suggest that insects manage these objectives of such open joints using a combination of cuticular microstructures and lubricating fluids. Here we provide an insight into the complex internal structure of the femoro-tibial joint of the black vine weevil, Otiorhynchus sulcatus. We apply a portfolio of tomography methods, such as X-ray micro- and nano-computed tomography and focused ion beam tomography, to analyse the different hierarchical levels, focusing, in particular, on the cuticle beneath the bearing surface. We provide a description of the gross morphology of the joint, reveal two different types of cuticular canals and document various cuticular surface patterns and microstructures. For the latter, we discuss their possible task in an autonomous cleaning process.