Problem Statement: Abalones are species of the genus Haliotis (Gastropoda: Archaeogastropoda: Haliotis) that are eaten in many countries. California is an important producer of abalones. In the 1990s farmed abalone in California were found to be growing more slowly than usual with grossly deformed shells. The deformed abalones could not be sold, and as the infestation spread, California’s abalone production, worth millions of dollars, was at risk.

Methods: The deformed abalone were found to be infested with a parasite, identified as a little known polychaete worm (Polychaeta: Sabellidae: Terebrasabella heterouncinata). The worm does not seriously harm the abalone, but the tunnels it builds deform the snail’s shell and cause it to grow more slowly. Information was urgently needed on whether other local mollusc fauna was at risk, and what countermeasures could be taken. The worm’s life cycle and its adaptation to parasitism were analysed and, to find out whether the parasite was a native or an introduced species, over 100 abalone shells in the Los Angeles County Museum for Natural History were examined to see if previous generations of molluscs had been affected.

Outcomes and Impacts: None of the museum specimens showed the characteristic tunnels left by the worm, which meant it was not a native but a newly introduced species. A worldwide search in collaboration with curators of other taxonomic collections revealed that the worm originated from Southern Africa. Unfortunately, no natural enemies of the parasite were found. Furthermore, taxonomic and other biological research revealed that infection occurred through the water; it did not require direct contact between the snails. It was therefore recommended to immediately cull all infected snails and annually clean abalone tanks at risk of infestation. More than 1.5 million infected animals were culled. Effective control of the parasitic worm minimised economic losses to abalone aquaculture in California, an industry worth several million dollars per year.

Lessons: International taxonomic research, including the use of archived materials from reference collections, allowed an effective parasite management strategy to be developed.