Convergent evolution of failure- and wear-prevention in radulae of rock-scraping land snails (Chondrinidae, Gastropoda)

This study investigates the morphology, material, and mechanical
properties of radular teeth in six lineages of Chondrinidae, a family of
terrestrial gastropods. We examined three species that forage on biofilms
from mixed substrates (Abida secale, Granopupa granum, Granaria frumentum)
and three that specialised in scraping lichen off rock faces (Chondrina
arcadica, Rupestrella rhodia, Solatopupa similis). Using scanning electron
microscopy (SEM), nanoindentation, and energy-dispersive X-ray
spectroscopy, we analysed tooth morphology, hardness H, Young’s modulus E,
and elemental composition. Our findings confirm that the central radular
region reflects substrate preferences, with rock-scraping species
exhibiting reduced tooth denticles and significantly higher E and H values
compared to mixed substrate feeders. Correlations between mechanical
properties and elemental composition (increased calcium or silicon
content) suggest convergently evolved strengthening mechanisms in
rock-scraping species. The results support hypotheses of parallel
evolution in radular adaptations, highlighting Chondrinidae as a valuable
model for studying the interplay of morphology, function, ecology, and
evolution.