Peacock Worm

• The crown is not just a filter: it sorts the captured particles by size, uses the edible ones and puts the sand grains towards building the tube.
• At the shadow of a predator it withdraws the crown into the tube in a fraction of a second, a reflex triggered by simple changes in light.
• If it loses the whole crown, it regrows it within a few weeks.
• Its crown of radioles, spread fanwise and often banded with colour, gives it the name peacock worm. It is the only part visible: the body stays inside the tube at all times.
• The tube is soft, made of mud and mucus rather than lime, and flexible; if removed from it, the worm can build a new one.
• It filters plankton with the cilia on its radioles and sorts what it catches into three sizes: the fine material goes to the mouth, the medium is discarded, and sand grains are kept for tube building.
• It has primitive compound eyes scattered along its radioles that detect nothing but shadows. That is enough: it withdraws into the tube in a fraction of a second when something passes overhead.
• It can regrow the entire crown if it loses it, which happens often because fish eat it.

Skeleton type

Invertebrate - no rigid skeleton (annelid)

Habitat and environment

Muddy, sandy and rocky bottoms of the north-eastern Atlantic and the Mediterranean, from 0 to 60 m

Sources consulted: Linneo (1767) · Marine Life Information Network · Nicol (1950), estudios sobre respuesta de sobresalto en Sabella · ScienceDirect (Hughes 1989) · Science Advances, How colonial animals evolve · Wikipedia, Zooid