Scaleworms

Scaleworms (Family Polynoidae) are a unique group of polychaetes whose dorsa (backs) are covered by pairs of scale-like structures called elytra. The elytra are mounted on elytrophores (short stalks). Elytra are not found on every segment of the body (more or less on alternate segments), but generally the number of pairs of elytra is the same within a scaleworm genus. Scaleworms are carnivores, feeding on small arthropods, snails, polychaetes, sponges and hydroids. Immediately upon metamorphosis from a swimming planktonic larva to a bottom-dwelling juvenile (with only five or six pairs of scales), it becomes carnivorous. Many scaleworms are free-living, but others are commensal: living in an association with another creature whereby neither is harmed, but at least one receives some benefit.