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   Ceratostoma inornatum (mollusc)   
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    Taxonomic name: Ceratostoma inornatum (Recluz, 1851)
    Synonyms: Ocenebra japonica (Dunker, 1860), Ocinebrellus inornatus (Recluz, 1851)
    Common names: Asian drill, Asian oyster drill, Japanese oyster drill
    Organism type: mollusc
    Ceratstoma inornatum is an oyster driller that destroys populations of oysters, especially that of Crassostrea gigas. In stocked populations though it causes 25% mortality. It is native to Asia and was introduced to the west coast of USA and the Atlantic coast of France.
    Ceratostoma inornatum has a narrow and elongated physiology (Berrouet al, 2004). It is around one inch (2.54cm) long. The radula is the band of teeth that acts as a "drill" to penetrate the shells of oysters (Vetmed, undated).
    Occurs in:
    estuarine habitats, marine habitats
    Habitat description
    Certostoma inornatum lives in cool waters (Berrouet al, 2004).
    General impacts
    Ceratostoma inornatum causes about 25% mortality in stocked oyster bed populations. Production costs increase (~20%) and the profits decrease (~55%) because of C. inornatum (Elston, 1997).
    Ceratostoma inornatum is a "threat to stocked and native oyster populations" (Ray, 2005). It is a prohibited species in the state of Oregon as of 1999 (Oregon, 2001) and in the state of Washington you need a permit to transport the species (Washington, undated). C. inornatum does not migrate by itself; it has to have another means of transport (Vetmed, undated).
    Geographical range
    Native range: Asia: Japan, Republic of Korea (Garcia-Meunieret al, undated)
    Known introduced range: Europe: France, USA: Washington, Oregon, California; Canada: British Columbia (Garcia-Meunieret al, 2002; USGS, 2005; Carlton, 1992)
    Management information
    Physical: The larvae of Ceratostoma inornatum that is found on the oyster, Crassostrea gigas, is killed by freshwater immersion (McEnnultyet al, 2001). It can also be controlled by quarantine because the larvae is not planktonic (Ray, 2005). Another method is to manually remove them by hand (Cheney and Booth, undated). Destroying the eggs of C. inornatum by burning is an effective means of control (Buhleet al, 2004; WGITMO, 2003). Using a screwdriver is a good way to get the eggs off oyster shells (White, 2007).
    Ceratostoma inornatum tends to feed on young oysters such as Crassostrea gigas (Ray, 2005). C. inornatus uses its radular which acts as the drill, and "it secretes digestive enzymes into the hole, through which the snail sucks up the partially liquefied flesh." It eats about 3 oysters per week (White, 2007).
    Certastoma inornatum produces multiple eggs on the sea floor (Buhleet al, 2004) and in the cracks of oyster shells (White, 2007). This is done between the months of April and July (White, 2007). Ten juvenile eventually emerge from each egg and they are 2mm in size. Reproductive size is 27mm and is reached a year after they emerge from the eggs (Buhleet al, 2004).
    Lifecycle stages
    Ceratostoma inornatum has two lifecycle stages. First, clumps of bright-yellow eggs are layed on the sea floor. When ready, juveniles will emerge and continue to grow (>2mm/month). Reproductive size is reached after about a year. Adult survival is ~30%. (Buhleet al, 2004).
    Principal sources: Carlton, J. 1992. Introduced Marine and Estaurine Mollusks of North America: An End-of-the-20th-Century Perspective. Journal of Shellfish Research. 11(2): 489-505.; Berrou V., Merle D., Dommergues J.-L., Crônier C. & Néraudeau D. 2004. — Comparative morphology of Pliocene, Quaternary and Recent shells of Ocenebra erinaceus (Linnaeus,1758) and O. brevirobusta Houart, 2000 (Mollusca, Muricidae, Ocenebrinae): reflections on the intra- and interspecific variations. Geodiversitas 26 (2) : 263-295.
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Friday, 3 August 2007

ISSG Landcare Research NBII IUCN University of Auckland