Radiole

A radiole is a heavily ciliated feather-like tentacle found in highly organized clusters on the crowns of Canalipalpata.

The animal can extend the crown from its calcareous tube for feeding and gas exchange, and rapidly retract it when disturbed or threatened.

Each of these bundles consists of a single row of radioles attached to a branchial stalk and curved into a semicircle.

[4] An adult worm typically has about 40 radioles in its crown, covered by tiny, hair-like branches called cilia.

When extended, these heavily ciliated radioles trap particles of organic matter and transport them towards the mouth.

The ventral surface of each radiole is covered by cilia that rhythmically move in such a way as to create a current in the surrounding water column.

This current carries planktonic particles from the underside of the crown upwards through the net of radioles to the dorsal surface.

Canalipalpata worms often lose one or more radioles, or even the entire crown as a result of predation by other animals or other types of trauma.

Some species even appear to have the ability to control the loss of their tentacular crowns, in much the same manner as when a lizard loses its tail.