PERNET, Bruno; Friday Harbor Laboratories, Washington: Evolutionary persistence of feeding structures in nonfeeding annelid larvae

The requirement for feeding during the larval stage has been lost in many lineages of marine invertebrates. This evolutionary transition in nutritional mode is often followed rapidly by changes in larval morphology, in particular reduction or loss of structures involved in feeding. Larvae of some sabellid annelids are unusual in that they possess functional particle capture systems (opposed bands of cilia) though they cannot ingest captured particles. These larvae probably lost the ability to ingest particles sometime in the Paleozoic, which leads one to wonder why they have not yet lost the ability to capture particles. I use observations on the development and functional biology of several sabellids to address hypotheses on this unexpected persistence of ancestral feeding structures in nonfeeding larvae.