Surface quantification of the wood-abrasive shell regions of the shipworm Teredo navalis indicates functional differentiation

Abstract Wood-boring shipworms are notorious for their destructive activity, using specialized calcareous valves with denticulate surface ornamentations to bore into wood. While the general morphology of shipworm shells has been well-studied, detailed quantitative analyses of their surface morphometrics and topography have not been undertaken. This exploratory study examined the structural details of the shell surfaces of the shipworm Teredo navalis , focusing on two anterior shell regions involved in wood abrasion: the anterior lobe (AL) and anterior median lobe (AmL). Using 2D and 3D imaging, the ornament morphology and surface topography were analyzed qualitatively and quantitatively. The findings revealed distinct differences in the shape and size of ornamentation between the two shell regions, supporting their functional specialization. Topographic analyses reflected peak-dominated and less abrupt surface textures on the AL, exhibiting considerably greater surface roughness than the valley-dominated surface with steeper peaks on the AmL. These differences indicate functional specialization. The AL resembles a serrated file tool, while the AmL functions as a rasp-like tool, highlighting their roles in different stages of the wood-boring process.