Substrate Roughness Induced Wear Pattern in Gastropod Radulae

Determining a precise contact area between one surface and another surface is essential for understanding tribological tool performance, since this area contributes to the force transmission. Radular teeth are part of the complex molluscan feeding apparatus acting on the ingesta by transmitting muscle-driven forces, in some cases working as a puncturing tool. Various approaches aimed at identifying the contact areas and cutting edges of radular teeth to understand the relationship between both shape and position of teeth and the function. However, most previous studies rely on feeding tracks which are difficult to interpret. To determine load transmitting regions, we here present an easy experimental set-up involving sandpaper that can be applied to a variety of molluscan species. Stylommatophoran gastropods were fed with food paste attached to sandpapers of different roughness for 1 month: subsequently, the radular tooth wear was analysed qualitatively. These feeding experiments under controlled conditions were performed for molluscan radula for the first time revealing distinct sandpaper-induced facets. Comparisons of the tooth material loss led to the determination of the contact areas and the amount of teeth involved in the feeding process, both directly related with the surface roughness. Additionally, the direction of force during feeding was reconstructed. The analyses of wear patterns resulting from the impact of teeth on the sandpaper grains contribute to our knowledge about the underlying mechanisms preventing structural failure in radulae. These mechanisms are based on the biomechanical behaviour of the radular supporting structures.