Functional Morphology of Eunicidan (Polychaeta) Jaws

Polychaetes exhibit diverse feeding strategies and diets, with some species possessing hardened teeth or jaws of varying complexity. Species in the order Eunicida have complex, rigid, articulated jaws consisting of multiple pairs of maxillae and a pair of mandibles. While all Eunicida possess this general jaw structure, several characteristics of the jaws vary considerably among families. These differences, described for fossilized and extant species’ jaws, have been used to infer evolutionary relationships. Little has been done, however, to relate jaw functional morphology and feeding behavior to diet. To explore these relationships, we compared the jaw kinematics and morphology of two distantly related eunicidan taxa with superficially similar jaw structures: Diopatra spp. (Onuphidae), predominantly herbivorous and tube dwelling, and Lumbrineris spp. (Lumbrineridae), a burrowing carnivore. Jaw kinematics were observed by filming individuals biting in a number of orientations. Some differences in jaw structure and kinematics between Diopatra spp. and Lumbrineris spp. can be interpreted to be consistent with their differences in diet. Relating jaw morphology to diet would improve understanding of early annelid communities by linking fossil teeth (scolecodonts) to the ecological roles of extant species with similar morphologies.