Am. Kuris et Cs. Culver, An introduced sabellid polychaete pest infesting cultured abalones and itspotential spread to other California gastropods, INVERTEBR B, 118(4), 1999, pp. 391-403
In 1993 an unusual sabellid polychaete was brought to our attention. It gro
ssly deformed the shells of cultured abalones in some of the California aba
lone mariculture facilities. This worm is not native to California and was
subsequently found in rocky intertidal and subtidal habitats in southern Af
rica, where it had not previously been recognized. The worm is hermaphrodit
ic and has benthic larvae that are competent to settle within 12 h and soon
secrete a mucous sheath. Development of the tentacular crown occurs within
a week and generation time can be short, about one month. The worm has a u
nique association with host gastropods. Unlike all other known shell-foulin
g organisms, the sabellid routinely settles inside the aperture at the grow
ing edge of the shell. The host responds by secreting a layer of nacre over
the mucous sheath to form a tube enclosing the worm, whose crown of tentac
les extends through the opening of the tube to the outer surface of the she
ll. Heavy infestations cause the cessation of linear growth of the host as
prismatic shell deposition cannot be resumed after repeated settlement of l
arvae. The sabellid is not very host specific; many other California native
gastropods are readily infested. Bivalves do not appear to be susceptible.
Efforts to find a native California predator of the adult worms were not s
uccessful. The sabellid has caused great economic damage to some facilities
commercially culturing abalones. An established population of this worm ha
s been detected in California, and further risk of establishment and spread
of this worm is great. Its unique biology:suggests that it may be a useful
experimental probe for studies of molluscan shell deposition and may also
serve to reveal how molluscs defend themselves against organisms attempting
to settle in and foul their apertures.