Ocinebrellus inornatus - Japanese oyster drill

The Japanese oyster drill is naturally found in the temperate seas of Northeast Asia, ranging from the coasts of northern China, Japan, and Korea to the Russian Sakhalin and the Kuril Islands. This natural range largely overlaps with that of the Japanese oyster, Crassostrea/Magallana gigas, which is the primary prey of the oyster drill and also a non-native species in Belgian waters ^[2-4].

First observation in Belgium

The Japanese oyster drill has not yet been observed in Belgium.

Distribution in Belgium

The Japanese oyster drill has not yet been observed in Belgium.

Distribution in neighbouring countries

In 1995, the species was first detected in French waters, in the Bay of Marennes-Oléron near La Rochelle ^[5,6]. Since then, its distribution has expanded northward to Brittany (Gulf of Morbihan) ^[7] and Normandy (Mont-Saint-Michel) ^[8]. Genetic studies have shown that the source population of these snails is located in the United States ^[9,10], where the species established itself in the early 20th century through oyster transport ^[11]. The species has also been observed in southern Portugal (Algarve) ^[12] and in the Danish Limfjord ^[2], respectively since 1999 and 2009, with the Danish population likely originating from the French ^[13]. Additionally, the Japanese oyster drill has been found in the Eastern Scheldt (the Netherlands) since 2007 ^[14], with the population growing annually between 2007 and 2009 ^[15].

The spread of the Japanese oyster drill outside its natural range is facilitated by aquaculture activities. For instance, the introduction into the Bay of Marennes-Oléron can be directly linked to the import of the Japanese oyster, Crassostrea/Magallana gigas, from the previously colonised British Columbia (Canada) ^[2,9]. Given the species' relatively limited natural dispersal ability, its secondary spread in Western Europe, including Brittany, the Netherlands, and elsewhere, is also associated with shellfish transport ^[2,16].

The Japanese oyster drill can thrive within a broad range of temperature and salinity conditions. The species is capable of surviving not only in open marine systems but also in fjord systems with salinities as low as 23 psu ^[2]. Reduced water temperatures down to 0-1°C during winter months do not appear to hinder the species ^[15]. This is not surprising, as the species is exposed to similar temperatures in its natural range around the Sea of Japan and the coasts of Sakhalin, allowing it to easily tolerate the sea water temperatures of the North Sea and southern Scandinavia ^[2].

Unlike many other marine non-native species, the Japanese oyster drill does not have a free-swimming larval stage. This characteristic, combined with its relatively low reproductive rate ^[2], means that its natural dispersal ability is somewhat limited ^[16-18]. However, when evaluating potential future spread, it should be noted that, although the Japanese oyster is the primary food source, the Japanese oyster drill is capable of switching to other prey species and can also survive on a diet of common mussels ^[2]. Nevertheless, the presence of large quantities of oysters is considered important for the establishment of the species ^[17]. Additionally, it is believed that the species avoids areas with significantly reduced salinity, such as estuarine zones ^[18].

Due to its flexibility in prey consumption (including oysters, mussels, cockles, gastropods, and barnacles), the Japanese oyster drill can cause ecological and economic damage, particularly to aquaculture facilities focused on shellfish farming. This species, and oyster drills in general, are known for their destructive predation on commercially valuable bivalves ^[17,18]. Eradication efforts for established populations in shellfish cultures using mechanical and suction dredging ^[19], trap setting (labor-intensive) ^[20], and chemical control (which impacts oysters and/or the environment) ^[19,21] have so far been unsuccessful. Immersion in freshwater seems to kill the oyster drill ^[13], but the tolerance of the Japanese oyster drill to low salinities is highly location-dependent ^[22]. For example, exposing oysters from the Eastern Scheldt to freshwater for 24 hours was not sufficient to cause damage to Japanese oyster drills adapted to the environmental conditions in the Eastern Scheldt ^[23].

However, management measures are in place. Adaptive cultivation methods are sometimes employed to prevent predation, such as the ‘off-bottom’ method, where young oysters are grown in suspended trays or bags (away from the bottom). This approach, while effective, incurs significant costs ^[13], as proactive control measures for fouling need to be specifically invested in high-growth areas. If not managed, fouling organisms may deplete the nutrients in the water that oysters rely on ^[24]. When opting for labor-intensive manual control of the oyster drill population, removing the eggs of the drill is preferred, as this method is more effective than removing adult individuals ^[17,25].

The most effective strategy against the spread of the Japanese oyster drill involves preventive measures through stringent regulations and inspections prior to shellfish transport.

The Japanese oyster drill is a carnivorous snail belonging to the family Muricidae. Its shell is spiral, right-handed, reaching a height of up to 48 mm, with a small apex at the end. Adult specimens have five complete whorls, with the final whorl characterised by four to twelve axial ribs. The inside of the outer lip of the aperture often features five small tooth-like structures. The siphonal canal is short ^[26]. The shell color varies from beige to brown, but can also be orange or striped ^[17]. A key feature often used to identify members of the Muricidae family is the presence of a labral tooth. However, this is not always present in the Japanese oyster drill ^[26], which has led to past misidentifications of the species ^[17].

Prior to laying eggs, the snails congregate in large numbers during the breeding season. Females produce clusters of 20 to 40 bright yellow egg capsules, each containing several hundred so-called 'nurse eggs', resulting in the production of only 10 to 15 embryos. The juveniles do not have a planktonic life stage and settle directly on the bottom, reaching sexual maturity after 1 to 2 years ^[2,27]. Research in North America has shown that the annual survival rate of adult individuals is only about 10 to 30% ^[27].

The Japanese oyster drill has chemoreceptive mechanisms that respond to the effluents (waste products) of its potential prey, allowing it to detect healthy prey ^[28]. Once on the prey, it creates a circular hole in the shell using an acid and its toothed tongue (radula), then sucks out the prey using a proboscis-like structure. This process takes about 5-6 days for mussels and cockles, and up to 2 weeks for Japanese oysters ^[29].

[1]          World Register of Marine Species (WoRMS) (2024). Ocinebrellus inornatus (Récluz, 1851). https://www.marinespecies.org/aphia.php?p=taxdetails&id=578702 (2024-10-18). 

[2]          Lützen, J.; Faasse, M.; Gittenberger, A.; Glenner, H.; Hoffmann, E. (2012). The Japanese oyster drill Ocinebrellus inornatus (Récluz, 1851) (Mollusca, Gastropoda, Muricidae), introduced to the Limfjord, Denmark. Aquat. Invasions 7(2): 181-191 [https://www.vliz.be/nl/imis?module=ref&refid=208199] 

[3]          Choe, B.L.; Park, J.-K. (1997). Description of muricid species (gastropoda: Neogastropoda) collected from the coastal areas of South Korea. Korean Journal of Biological Sciences 1(2): 281-296. [https://www.vliz.be/en/imis?module=ref&refid=381420] 

[4]          Garcia-Meunier, P.; Martel, C.; Trichet, C. (2003). Comparisons of demographic features of an invasive species, Ocinebrellus inornatus, versus an indigenous species, Ocenebra erinacea, in: Third International Conference on Marine Bioinvasions March 16-19, 2003 convened at Scripps Institution of Oceanography, La Jolla, California: abstract book. pp. 43. [https://www.vliz.be/en/imis?module=ref&refid=391071] 

[5]          de Montaudouin, X.; Sauriau, P.-G. (2000). Contribution to a synopsis of marine species richness in the Pertuis Charentais Sea with new insights in soft-bottom macrofauna of the Marennes-Oleron Bay. Cah. Biol. Mar. 41(2): 181-222 [https://www.vliz.be/nl/imis?module=ref&refid=66969] 

[6]          Pigeot, J.; Miramand, P.; Garcia-Meunier, P.; Guyot, T.; Séguignes, M. (2000). Présence d’un nouveau prédateur de l’huître creuse, Ocinebrellus inornatus (Récluz, 1851), dans le bassin conchylicole de Marennes-Oléron. C. R. Acad. Sci., Sér. 3 Sci. Vie 323(8): 697-703. [https://www.vliz.be/en/imis?module=ref&refid=391073] 

[7]          Goulletquer, P.; Bachelet, G.; Sauriau, P.G.; Noel, P. (2002). Open Atlantic coast of Europe: a century of introduced species, in: Leppäkoski, E. et al. (Ed.) Invasive aquatic species of Europe: distribution, impacts and management. pp. 276-290. [https://www.vliz.be/nl/imis?module=ref&refid=40609] 

[8]          Delongueville, C.; Scaillet, R. (2007). Ocinebrellus inornatus (Ocenebra inornata) (Récluz, 1851) en baie du Mont-Saint-Michel (France). Novapex (Jodoigne) Société 8(3): 96-99. [https://www.vliz.be/nl/imis?module=ref&refid=232707]

[9]          Martel, C.; Viard, F.; Bourguet, D.; Garcia-Meunier, P. (2004). Invasion by the marine gastropod Ocinebrellus inornatus in France: I. Scenario for the source of introduction. J. Exp. Mar. Biol. Ecol. 305(2): 155-170. [https://www.vliz.be/en/imis?module=ref&refid=381322] 

[10]        Martel, C.; Guarini, J.-M.; Blanchard, G.; Sauriau, P.G.; Trichet, C.; Robert, S.; Garcia-Meunier, P. (2004). Invasion by the marine gastropod Ocinebrellus inornatus in France. III. Comparison of biological traits with the resident species Ocenebra erinacea. Mar. Biol. (Berl.) 146(1): 93-102. [https://www.vliz.be/en/imis?module=ref&refid=381660] 

[11]        Wolff, W.J.; Reise, K. (2002). Oyster imports as a vector for the introduction of alien species into northern and western European coastal waters, in: Leppäkoski, E. et al. (Ed.) Invasive aquatic species of Europe: Distribution, impacts and management. pp. 193-205. [https://www.vliz.be/nl/imis?module=ref&refid=40600] 

[12]        Afonso, C.M.L. (2011). Non-indigenous Japanese oyster drill Pteropurpura (Ocinebrellus) inornata (Récluz, 1851) (Gastropoda: Muricidae) on the South-west coast of Portugal. Aquat. Invasions 6(Supplement 1): S85-S88. [https://www.vliz.be/en/imis?module=ref&refid=381251] 

[13]        Fey, F.; Van den Brink, A.M.; Wijsman, J.W.M.; Bos, O.G. (2010). Risk assessment on the possible introduction of three predatory snails (Ocinebrellus inornatus, Urosalpinx cinerea, Rapana venosa) in the Dutch Wadden Sea. IMARES Wageningen Report, C032/10. IMARES Wageningen UR: IJmuiden. 88 pp. [https://www.vliz.be/en/imis?module=ref&refid=381424] 

[14]        Goud, J.; Titselaar, F.F.L.M.; Mulder, G. (2008). Weer een ‘verstekeling’: de Japanse Stekelhoren Ocinebrellus inornatus (Récluz, 1851) (Gastropoda, Muricidae) levend aangetroffen in de Oosterschelde. Spirula 365: 134-136. [https://www.vliz.be/en/imis?module=ref&refid=381427] 

[15]        Faasse, M.; Ligthart, M. (2009). American (Urosalpinx cinerea) and Japanese oyster drill (Ocinebrellus inornatus) (Gastropoda: Muricidae) flourish near shellfish culture plots in The Netherlands. Aquat. Invasions 4(2): 321-326. [https://www.vliz.be/en/imis?module=ref&refid=381265] 

[16]        Martel, C.; Viard, F.; Bourguet, D.; Garcia-Meunier, P. (2004). Invasion by the marine gastropod Ocinebrellus inornatus in France. II. Expansion along the Atlantic coast. Mar. Ecol. Prog. Ser. 273: 163-172. [https://www.vliz.be/en/imis?module=ref&refid=381326] 

[17]        Duckwall, L. (2009). Pacific Northwest aquatic invasive species profile. Japanese oyster drill Ocinebrellus inornatus. [S.n.]: [s.l.]. 12 pp. [https://www.vliz.be/en/imis?module=ref&refid=381423] 

[18]        Buhle, E.R.; Ruesink, J.L. (2009). Impacts of invasive oyster drills on Olympia oyster (Ostrea lurida Carpenter 1864) recovery in Willapa Bay, Washington, United States. J. Shellfish Res. 28(1): 87-96. [https://www.vliz.be/en/imis?module=ref&refid=381246] 

[19]        Locke, A. (2009). Rapid response to non-indigenous species. 1. Goals and history of rapid response in the marine environment. Aquat. Invasions 4(1): 237-247. [https://www.vliz.be/en/imis?module=ref&refid=381245] 

[20]        Eno, N.C.; Clark, R.A.; Sanderson, W.G. (Ed.) (1997). Non-native marine species in British waters: a review and directory. Joint Nature Conservation Committee: Peterborough. ISBN 1-86107-442-5. 152 pp. [https://www.vliz.be/nl/imis?module=ref&refid=24400] 

[21]        McEnnulty, F. R.; Bax, N.J.; Schaffelke, B.; Campbell, M.L. (2001). A review of rapid response options for the control of ABWMAC listed introduced marine pest species and related taxa in Australian waters. Technical report (Centre for Research on Introduced Marine Pests (Australia)), 23. CSIRO Div. Marine Research. Centre for Research on Introduced Marine Pests: Hobart. ISBN 0643062513. 110 pp. [https://www.vliz.be/nl/imis?module=ref&refid=391242] 

[22]        Federighi, H. (1931). Salinity death-points of the oyster drill snail, Urosalpinx cinerea Say. Ecology 12(2): 346-353. [https://www.vliz.be/en/imis?module=ref&refid=381327] 

[23]        van den Brink, A.; Wijsman, J.W.M. (2010). Freshwater immersion as a method to remove Urosalpinx cinerea and Ocinebrellus inornatus from mussel seed. IMARES Wageningen Report, C020/10. IMARES Wageningen UR: IJmuiden. 15 pp. [https://www.vliz.be/en/imis?module=ref&refid=381422] 

[24]        Walton, W.C.; Davis, J.E.; Chaplin, G.I.; Rikard, F.S.; Hanson, T.R.; Waters, P.J.; LaDon Swann, D. (2012). Off-bottom oyster farming. Alabama A&M/Auburn University: United States. 8 pp. [https://www.vliz.be/en/imis?module=ref&refid=391048] 

[25]        Buhle, E.R.; Margolis, M.; Ruesink, J.L. (2005). Bang for buck: cost-effective control of invasive species with different life histories. Ecol. Econ. 52(3): 355-366. [https://www.vliz.be/en/imis?module=ref&refid=381328] 

[26]        Amano, K.; Vermeij, G.J. (1998). Taxonomy and evolution of the genus Ocinebrellus (Gastropoda : Muricidae) in Japan. Paleontological Research 2(3): 199-212. [https://www.vliz.be/en/imis?module=ref&refid=381329] 

[27]        White, C. (2007). WSG-funded researcher takes on Willapa’s troublesome oyster drills. Sea Star Winter 2007: 1-2. [https://www.vliz.be/en/imis?module=ref&refid=391075] 

[28]        Colakovic, B. (2018). Investigating the behavior of the invasive marine species the Japanese Oyster Drill (Ocinebrellus inornatus): Food preference, and Behaviour. HZ University of Applied Sciences: Vlissingen. 26 pp. [https://www.vliz.be/en/imis?module=ref&refid=391076] 

[29]        Chew, K.K.; Eisler, R. (1958). A preliminary study of the feeding habits of the Japanese oyster drill, Ocinebra japonica. J. Fish. Res. Bd. Can. 15(4): 529-535. [https://www.vliz.be/en/imis?module=ref&refid=381330]

VLIZ Alien Species Consortium (2024). Ocinebrellus inornatus – Japanese oyster drill. Introduced alien species of the Belgian part of the North Sea and adjacent estuaries anno 2024. Flanders Marine Institute (VLIZ). 6 pp.