Alternative common names:
The shell worm is an alien species from the Pacific Ocean around North America that has been introduced to the Atlantic Ocean on the West Coast of South Africa. This is the main pest species on farmed abalone in South Africa. Molecular studies have indicated that shell worm was moved between farms through the movement of infested abalone.
Where does this species come from?
Canada (British Columbia) to southern California.
What is its invasive status in South Africa?
NEMBA Category 1b.
Where in South Africa is it a problem?
Mostly along the West Coast of the Western Cape (St. Helena Bay to Haga Haga on on-shore abalone culture facilities, Saldanha Bay & Walker Bay in sediment in intertidal zone) and Northern Cape.
How does it spread?
Molecular studies indicate that it was moved between farms through the movement of infested abalone.
Why is it a problem?
It is the leading pest species on farmed abalone because it reduces the condition of cultured abalone and increase production costs. It also invades intertidal benthic rocky shores, and builds reefs formed by thousands of individuals.
What does it look like?
Description: A small tube-dwelling marine worm with a length of about 20mm. The body is yellow when alive with conspicuous red blood vessels. The tail has a rounded disc with a notch.
Habitat: Inhabits sediment and calcareous substrates. Borer on cultured abalone. In extreme cases may form ‘mudpacks’ formed inside the shell where the abalone tries to isolate itself from the accumulated sediment. It usually houses many worms and often causes the shell to break along the respiratory pores.
Breeding: Worms reproduce throughout the year, but increased numbers from the end of winter to early summer.