Shell-burrowing Sponges of Scallops


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Shell-burrowing or Shell-boring sponges, Clionids.

Scientific name or taxonomic affiliation

Clionid sponges, most commonly Cliona spp. (e.g. Cliona vastifica, Cliona celata).

Geographic distribution

East and west coasts of Canada and Sea of Japan. Probably ubiquitous.

Host species

Placopecten magellanicus, Patinopecten yessoensis as well as other surface dwelling molluscs including oysters and mussels.

Impact on the host

Penetrates the periostracum forming holes in the outer surface and a tunnel network throughout the shell. Scallops may successfully wall off any openings that penetrate through the inner nacre to the soft tissues. If perforation interferes with adductor muscle attachment, impaired feeding causes mortalities. Sponge tunnels may become inhabited by other organisms, such as polychaete worms, and chronic soft-tissue irritation may result in secondary bacterial or fungal infections. Scallop responses to such damage are energetically costly and chronic perforation can cause significant weakening and death. Also, associated lesions in the soft tissues may become visible in the adductor muscle rendering affected scallops unmarketable. Smaller scallops appear less affected by shell penetration than larger individuals.

Diagnostic techniques

Gross Observations: Round holes (generally smaller than 2-3 mm in diameter depending on the species involved) on the surface of the shell. Inner shell surface may show the presence of dark spots or bumps, depending on the degree of penetration by the sponge. The sponge may be yellow or green in colour.

Methods of control

Shell damage is most easily reduced or prevented by growing scallops off bottom (i.e. hanging culture).


Ball, M.C. and S.E. McGladdery. 2001. Scallop parasites, pests and diseases: implications for aquaculture development in Canada. Bulletin of the Aquaculture Association of Canada 101-3: 13-18.

Evans, J.W. 1969. Borers in the shell of the sea scallop Placopecten magellanicus. American Zoologists 9: 775-782.

Kurochkin, Y.V., E.M. Tsimbalyuk and A.V. Rybakov. 1986. Parazitî i bolyezni. (Parasites and diseases.) In: P.A. Motavkin (ed.). Primorskii grebeshok. (The Yezo scallop or Japanese common scallop Mizuhopecten yessoensis (Jay).) Institute of Marine Biology, Far East Science Centre, Academy of the USSR, Vladivostok, p. 174­182. (In Russian).

Lauckner, G. 1983. Diseases of Mollusca: Bivalvia. In: O. Kinne (ed.). Diseases of Marine Animals. Volume II: Introduction, Bivalvia to Scaphopoda. Biologische Anstalt Helgoland, Hamburg, p. 617-626.

Medcof, J.C. 1949. Dark-meat and the shell disease of scallops. Progress Report Atlantic Coastal Stations No. 45: 3-6.

Merril, A.S. 1961. Some observations of the growth and survival of organisms on the shell of Placopecten magellanicus. Annual Report American Malacological Union. Bulletin No. 28: 4-5.

Sindermann, C.J. 1971. Predators and diseases of commercial marine Mollusca of the United States. Report American Malacological Union 1970: 35-36

Citation Information

Bower, S.M., McGladdery, S.E. (2004): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Shell-burrowing Sponges of Scallops.

Date last revised: July 2004
Comments to Susan Bower

Date modified: