Shell-boring Polychaetes of Abalone


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Shell-boring polychaetes, Blister worms, mudworms.

Scientific name or taxonomic affiliation

Polydora spp. (possibly P. limicola, P. ligni and/or P. websteri), Polydora hoplura, Polydora woodwicki, Dipolydora armata, Boccardia knoxi and possibly other polychaete species in the family Sipionidae.

Geographic distribution

Global, although some species probably have limited distributions. Specific problems have been reported in the following locations: southern Japan; South Africa; Victoria, Australia; Port Neville Inlet in British Columbia, Canada; and abalone farms in Tasmaina, Australia; New Zealand; and China.

Host species

Haliotis kamtschatkana, Haliotis diversicolor, Haliotis midae, Haliotis iris and other species of abalone as well as various species of bivalves that live on the surface of the substrate including oysters, mussels and scallops.

Impact on the host

Most infestations are innocuous and are usually of low intensity with polychaete burrows being confined to the shell. However, in southern Japan, the flesh weight of H. diversicolor aquatilis decreased significantly when infested with more than ten Polydora sp. per shell (Kojima and Imajima 1982). In South Africa, spionid polychaetes occur in high numbers on some farms and cause severe shell damage and stress to some H. midae by penetrating the mantle cavity (Ruck and Cook 1999, Simon et al. 2006). In one inlet in British Columbia (Port Neville), the shells of H. kamtschatkana were extensively riddled with a labyrinth of Polydora (possibly P. limicola, P. ligni and/or P. websteri) burrows resulting in fragile shells that cracked easily. The shells also had internal deformities such as nacre-covered nodules and patches of dark discolouration (Horne 1996). Two other species of spionid polychaetes (mudworms), Boccardia knoxi and Polydora hoplura, were associated with severe blistering in the shell and 50% or greater mortality among cultured abalone at several sea-based facilities in southern Tasmania, Australia (Lleonart et al. 2003b). In New Zealand, H. iris that hardoured P. hoplura (up to 7 per abalone) were all markedly underweight and the presence of the polycheate on the inside of the shell was associated with brown conchiolin deposits (Diggles and Oliver 2005).

Diagnostic techniques

Gross Observations: Hold clean shell against a bright light and examine through the shell matrix for sinuous burrows about 1 to 2 mm in diameter.

Wet Mounts: For specific identification the polychaete must be removed from the shell intact. Break the shell along the burrow using bone shears. Submerge the shell fragments in cool sea water and extract the intact living polychaete from the burrow with fine forceps and needle. McDiarmid et al. (2004) had success extracting the polychaetes by placing infected shells in a 50% alcohol, 50% seawater mix. Place the extracted worm on a piece of plasticine and, using pins positioned along the edges of the body to keep the worm straight, flood with 70% alcohol and store in 50-70% isopropyl alcohol. Note: these procedures are very labourious and time-consuming. For other techniques see Knudsen (1966).

X-rays: Burrow morphology can be determined by exposing infested shells to 30 Kv, 0.2mA for 12 seconds (McDiarmid et al. 2004).

Methods of control

High prevalence and intensity of infection have been associated with increased levels of organic pollution (Anger 1977, Rice and Simon 1980). This association was certainly true for the situation in British Columbia where poor water circulation caused by a narrow inlet into a fjord and nutrient-rich water resulting from logging activities probably induced abnormal proliferation of Polydora. The toxoglossan snail Oenopota levidensis (native to British Columbia and resides subtidally in the same zones as abalone) is a predator of Polydora spp. and may have the potential of being used as a method of biological control in abalone culture facilities. Lleonart (1999, 2001, 2003a) found that air drying (about 4 hr at 21 °C and about 60% humidity) of abalone from open water culture facilities in Tasmania significantly reduced infestation by both B. knoxi and P. hoplura with no apparent detrimental affects on the abalone. Also, preliminary field exposure results indicated that settlement by both these polychaetes occurred during a short dispersive period making farm management practices feasible for avoiding problems (Lleonart 1999). Nevertheless, it is important to minimize the presence of all shell-boring organisms from abalone aquaculture facilities.


Anger, K. 1977. Benthic invertebrates as indicators of organic pollution in the western Baltic Sea. Internationale Revue der Gesamten Hydrobiologie 62: 245-254.

Bower, S.M. 2000. Infectious diseases of abalone (Haliotis spp.) and risks associated with transplantation. In: Campbell, A. (Editor), Workshop on Rebuilding Abalone Stocks in British Columbia. Canadian Special Publication of Fisheries and Aquatic Sciences 130: In press.

Diggles, B.K. and M. Oliver. 2005. Diseases of cultured paua (Haliotis iris) in New Zealand. In: Walker, P.J., R.G. Lester, M.G. Bondad-Reantaso (eds.) Diseases in Asian Aquaculture V. Proceedings of the 5th Symposium on Diseases in Asian Aquaculture. Fish Health Section, Asian Fisheries Society, Manila. pp. 275-287.

Horne, G. 1996. KTFC abalone project report. Report submitted to Warren Nagata and the Kwakiutl Territorial Fisheries Commission. For a copy contact S.M. Bower. 33 pp.

Kojima, H. and M. Imajima. 1982. Burrowing polychaetes in the shells of the abalone Haliotis diversicolor aquatilis chiefly on the species of Polydora. Bulletin of the Japanese Society of Scientific Fisheries 48: 31-35. (In Japanese, with English abstract).

Knudsen, J.W. 1966. Biological Techniques - Collecting, Preserving, and Illustrating Plants and Animals. Harper and Row, New York. p. 157-160.

Lleonart, M. 1999. 1. Mud worm treatment trials and 2. Initial report: abalone mud worm field studies in infected and progression patterns. In: Abalone Aquaculture Sub-Program. Proceedings of the 6th Annual Abalone Aquaculture Workshop. World Aquaculture Society Conference, Sydney, April 1999. Fisheries Research & Development Corporation, Deakin, Australia pp 1-14.

Lleonart, M. 2001. Australian abalone mudworms: avoidance and identification. A farm manual. Web publication.

Lleonart, M., J. Handlinger and M. Powell. 2003a. Treatment of spionid mud worm (Boccardia knoxi Rainer) infestation of cultured abalone. Aquaculture 217: 1-10.

Lleonart, M., J. Handlinger and M. Powell. 2003b. Spionid mudworm infestation of farmed abalone (Haliotis spp.). Aquaculture 221: 85-96.

McDiarmid, H., R. Day and R. Wilson. 2004. The ecology of polychaetes that infest abalone shells in Victoria, Australia. Journal of Shellfish Research 23: 1179-1188.

Nie, Z. and S. Wang. 2004. The status of abalone culture in China. Journal of Shellfish Research 23: 941-945.

Rice, S.A. and J.L. Simon. 1980. Intraspecific variation in the pollution indicator polychaete Polydora ligni (Spionidae). Ophelia 19: 79-115.

Simon, C.A., A. Ludford and S. Wynne. 2006. Spionid polychaetes infesting cultured abalone Haliotis midae in South Africa. African Journal of Marine Science 28: 167–171.

Citation Information

Bower, S.M. (2009): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Shell-boring Polychaetes of Abalone.

Date last revised: May 2009
Comments to Susan Bower

Date modified: