Subfamily Spirorbinae
The subfamily Spirorbinae is a subset of the polychaete worms (marine worms). Spirorbin worms form a tiny, calcareous spiral shell which houses the animal. The worm can fully retract into the shell, or may extend its radioles (feathery appendages) to feed. One paddle-shaped radiole is used to close up the mouth of the shell when the worm is retracted.
Anatomy of Spirorbin worms
Radioles- feathery appendages which can extend from the mouth of the shell to collect food
Operculum- a modified radiole used to cover the mouth of the shell
Operculum- a modified radiole used to cover the mouth of the shell