Shell-burrowing Sponges of Oysters
Category 4 (Negligible Regulatory Significance in Canada)
Common, generally accepted names of the organism or disease agent
Shell-boring or shell-burrowing sponges, or clionid sponges.
Scientific name or taxonomic affiliation
Cliona spp. including Cliona celata, Cliona lobata, Cliona spirilla, Cliona truitti, and Cliona vastifica.
Global, although some species may have limited distribution.
Impact on the host
Boring sponges are primarily excavaters of calcareous materials to provide themselves with shelter and do not obtain nutrients directly from its host. Nevertheless, the sponge penetrates the periostracum forming holes in the outer surface and a tunnel network throughout the shell. Chronic invasion may result in penetration of the conchiolin layer and through to the inner surface. The oyster may successfully wall-off the nacreal opening made by the sponge, preventing entry of sand, mud or other irritants. If perforation exceeds shell repair, however, the oyster is weakened and interference with adductor muscle attachment impedes feeding and causes mortality. Sponge tunnels may become inhabited by other organisms, such as polychaete worms, which may reduce market value, but rarely impacts directly on oyster health. Smaller oysters appear less susceptible to shell penetration than thicker shelled individuals.
The Cliona sp. that invades the shells of Pinctada maxima in western Australia is capable of penetrating the outer prismatic and inner nacerous layers resulting in high mortalities of mature pearl oysters over a relatively short period of time. The apparent increase in the presence of this species is of concern to the successful operation of pearl oyster farms. Pearl production is seriously affected because infected pearl oysters expend more energy on depositing thickened nacre to protect themselves from the invading sponge instead of depositing nacre on the previously inserted pearl nuclei resulting in pearls with physical imperfections, discolourations and thus substantial decrease in quality. Often, invaded shells become weak and brittle, and the mantle retracts resulting in pearl oyster mortality (Moase et al. 1999).
Gross Observations: Round holes (generally less than 2-3 mm in diameter depending on the species involved) forming a "honeycomb" pattern on the outer surface of the shell. The sponge within the hole is often yellow in colour. Inner shell surface may show the presence of dark spots or bumps, depending on degree of penetration by the sponge.
Methods of control
Shell damage is most easily reduced by growing shellfish off bottom (i.e. hanging culture). The pearl oyster industry in Australia has had some success in reducing the impact of Cliona sp. infestations by "suffocation" of the sponge (Moase et al. 1999). Medcof (1961) indicated that immersing affected oysters for 5 minutes in a saturated brine solution (undissolved salt present in the bath) or soaking them for 12 to 16 hours in fresh water was effective in killing the sponge.
de Laubenfels, M. W. 1947. Ecology of the sponges of a brackish water environment at Beaufort, N.C. Ecological Monographs 17: 31-46.
Medcof, J.C. 1961. Oyster farming in the maritimes. Chapter 9.2 Boring Sponge. Bulletins of the Fisheries Research Board of Canada 131: 80-83.
Moase, P.B., A. Wilmont and S.A. Parkinson 1999. Cliona - an enemy of the pearl oyster, Pinctada maxima in the west Australian pearling industry. In: C.L. Browdy and R. Fletcher (co-program chairs). Book of Abstracts. The Annual International Conference and Exposition of the World Aquaculture Society, 26 April-2 May, 1999, Sydney, Australia. p. 522. (Abstract).
Old, M.C. 1941. The taxonomy and distribution of the boring sponges (Clionidae) along the Atlantic coast of North America. Chesapeake Biological Laboratory 44: 3-30.
Warburton, F. E. 1958. Boring sponges, Cliona species, of eastern Canada, with a note on the validity of C. lobata. Canadian Journal of Zoology 36: 123-125.
Bower, S.M. (2001): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Shell-burrowing Sponges of Oysters.
Date last revised: June 2001
Comments to Susan Bower
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