Symbiotic scale worm

Description:

Arctonoe vittata is a scale worm that typically lives on the underside of various invertebrates and has a commensal relationship with its host, defending it from would-be predators. A pale yellowish colour and can grow to a length of 8 to 10 cm (3 to 4 in) but is usually shorter. I was amazed at how the coloration was so similar to the limpet.

Habitat:

Spotted in a tide pool at low tide at Tongue Point Marine Sanctuary.

Notes:

The scale worm protects its host (in this case the Rough Keyhole limpet ( Diodora aspera) from starfish, such as Pisaster ochraceus, by biting the tube feet of the starfish, usually succeeding in driving it away. The worm is a predator, but does not attack its host, instead searching for prey to target as the limpet moves around.