Systematic characters of some polychaetes (Annelida) at the level of the chemical composition of the jaws

The mandibles and maxillae of the buccal ventral organ of 2 species of Eunicidae (Marphysa sanguinea and Eunice torquata) are highly calcified, in contrast to the jaws of 4 species of other families of ‘errant’ predacious Polychaetes (Nereidae, Nephthyidae, Aphroditidae and Glyceridae) with axial proboscis. The amino acid composition of the structural proteins of these buccal pieces is also different in the two groups. The structural proteins of the jaws of Glycera convoluta (Glyceridae) are essentially made up of glycine and histidine (up to 86 residues per 100 residues). These chemical characters confirm the phyletic relationships proposed by Dales.¹