The molluscs’ periodic table: Elemental analysis reveals distinct mineralization patterns in radular teeth

Abstract

The molluscan phylum is the second specious animal group inhabiting various habitats and feeding on a variety of food sources. The latter is enabled by the radula, a small chitinous membrane with embedded teeth, one important molluscan autapomorphy. Between species, radulae can vary in their morphology, mechanical, and chemical properties. With regard to radular chemical composition, some taxa (Polyplacophora and Patellogastropoda) were studied extensively in the past decades, due to their specificity to incorporate high proportions of iron, calcium, and silicon. There is, however, a huge lack of knowledge about radular chemical composition in other molluscan taxa. The work presented here aims at shedding light on the radular chemistry by performing energy-dispersive X-ray spectroscopy (EDX) analyses on overall 24 molluscan species, thereof two Polyplacophora, two Cephalopoda, and 20 Gastropoda. The elements, which are not part of chitin, and their proportions were documented for overall 1448 individual, mature teeth and hypotheses about potential biomineralizations types were proposed. The here presented work additionally comprises a detailed record on past studies about the chemical composition of molluscan teeth, which is an important basis for further investigation of the radular chemistry. The found disparity in elements detected, in their distribution and proportions highlights the diversity of evolutionary solutions, as it depicts multiple biomineralization types present within Mollusca.