Wear-coping mechanisms and functional morphology of the radular teeth of (Neritimorpha, Gastropoda).

In most molluscan species, the food is manipulated and taken in by the radula, a chitinous structure exhibiting diverse morphologies and compositions. The teeth of Patellogastropoda and Polyplacophora are well studied, with heavy mineralization reducing wear and failure. However, some gastropod taxa possess unmineralized teeth, even though they forage from rocks. This study characterizes the teeth of the gastropod as representative neritid species. Using a combination of techniques-scanning electron microscopy, confocal laser scanning microscopy, nanoindentation and energy-dispersive X-ray spectroscopy -the biomechanical and compositional properties of the teeth were examined. The heterogeneous presence of compositional gradients, together with previous wear analyses, renders the teeth to have different functions. Some teeth are involved in loosening food, collecting food particles or, as joints, spanning the radula in a certain configuration. A key finding was the presence of tooth coatings enriched with calcium (Ca) in regions prone to abrasion. The study also identified heterogeneities in autofluorescence patterns, which were directly associated with the distribution of Ca within the coatings and the degree of tanning. This study broadens our understanding of mechanical adaptation in gastropod feeding structures, showing that feeding from solid surfaces is also possible with partial and targeted reinforcement instead of full tooth mineralization-and that structure-function relationships are more diverse than previously thought.