Crepidula fornicata (American slipper limpet)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Latitude/Altitude Ranges
- Air Temperature
- Water Tolerances
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Economic Impact
- Environmental Impact
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Gaps in Knowledge/Research Needs
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Crepidula fornicata Linnaeus, 1758
Preferred Common Name
- American slipper limpet
Other Scientific Names
- Patella fornicata
International Common Names
- English: boat-shells; bungalows; slipper-limpet; thumbnails
Local Common Names
- : common Atlantic slippershell
- Denmark: toffelsnegl
- France: crépidule
- Germany: Pantoffelsnecke
- Netherlands: muiltje
- Sweden: toffelsnegl
- UK/England and Wales: oyster pest
Summary of InvasivenessTop of page
At the end of the nineteenth century, C. fornicata was accidentally introduced in Europe where it found favourable conditions to settle and develop: free surfaces of sandy-coarse sediment, optimal water temperature range, copious suspended organic matter as food and no specific predators; all this contributed to a rapid growth and reproductive success.
Oyster farming is the main cause of introduction and dispersal. Dredging and trawling of the oyster-growing areas has contributed to the spatial spread of C. fornicata. It is now demonstrated that these fishing practices have, for decades, played a main role in the spread.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Mollusca
- Class: Gastropoda
- Subclass: Caenogastropoda
- Order: Littorinimorpha
- Unknown: Calyptraeoidea
- Family: Calyptraeidae
- Genus: Crepidula
- Species: Crepidula fornicata
Notes on Taxonomy and NomenclatureTop of page
DescriptionTop of page
C. fornicata is a marine gastropod with a brown shell. Individuals reach about 6 cm long. The septum divides the interior of the shell into two parts: the external one where the foot and head can move and the internal one where the visceral mass is protected. Growth is rather rapid and a size of 2 cm is reached in 2 years. The plasticity of this species is important and shell can be deformed.
The first particularity of this species is that the individuals gather under attractive substances and form colonies, called ‘chains’. Individuals settle on top of each other, forming clusters. Only one juvenile remains at the top of the stack, the others move to form a new colony. The population extends in three dimensions.
In a standard colony there are 5 or 6 individuals, but in dense populations, this creates amazing numbers of stacks with complex colonies where the juveniles attach anywhere and support a new chain.
Newel and Kofoed (1977) described the morphology of the feeding system and measured the feeding rates in C. fornicata. This ubiquistous species ingests a wide variety of organic and inorganic food, at a rate of about 1 litre h-1 g-1, and also ingests some of its own larvae (Pechenik et al., 2004). The pelagic larva is also able to filter a wide range of particles (Blanchard et al., 2008). The radula can also capture some deposited matter. This feeding mode helps it find sufficient food to develop large populations, contrary to other grazing patellids (Hoagland, 1977).
Being fixed, the animals have developed a particular reproduction. The species is protandric. Juveniles are males and individuals become rapidly hermaphrodites from the second year, and then are females during the rest of their life (10 years). Between males and females of the same stack, fecundation is direct and sperm can be stored in a receptacle. Females of 2 cm long can be ovigerous. The brood is protected, eggs are laid grouped in bags (about 50 eggs bag-1) and are first stored near the head and later fixed on the lower shell. After about a month, each female releases 10-20,000 free larvae. They are veliger, barrel-shaped with a central ring of filaments to move in the plankton. Their size (min. 400 µm) and their strength make them suitable for experimental use (Pechenik and Lima, 1984; Pechenik et al., 2002b, 2004). The pelagic phase is about 3-weeks long (depending of the temperature) then larvae metamorphose and fall to the bottom where they look for suitable supports. All kinds of hard material can be used but they prefer a congener shell.
Being ubiquitous, eurythermic and euryhaline, this species can be observed in all kinds of environments: rocky, gravel or sandy bottoms, as well as in muddy areas where are measured the highest densities in Europe. These characteristics have helped it to spread so successfully.
DistributionTop of page
The geographical distribution of C. fornicata now stretches over 24 degrees of latitude, reaching all European seasides and the English Channel which currently appears to be the most colonized area (Blanchard, 1997). It is currently limited to the northern hemisphere. In the western USA, it was imported with oysters in Puget Sound during the 1930s, and is now common along the Washington state coastline (Hoagland, 1974, 1977). In 1968, spreading populations were noted in the bays of Tokyo and Sagami in Japan (Habe and Maze, 1970).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Japan||Present||Introduced||Invasive||Habe and Maze, 1970||In 1968 populations were noted in the bays of Tokyo and Sagami. Also found in Toyama Bay (S Kosuge, Institute of Malacology, Tokyo, personal communication, 1995)|
|-Honshu||Present||Introduced||Invasive||Habe and Maze, 1970||The western coast is colonized|
|-Shikoku||Present||Introduced||Invasive||Habe and Maze, 1970||All the coasts of the island are now colonized|
|Canada||Present||Walne, 1956||From Escuminac Point to the frontier of Antartic coast|
|-British Columbia||Localised||Introduced||Invasive||Wonham and Carlson, 2005|
|-New Brunswick||Present||Native||Not invasive||Walne, 1956||Escuminac Point 47 degrees North|
|-Nova Scotia||Present||Native||Dickinson et al., 1999|
|-Prince Edward Island||Present||Native||Not invasive||Provancher, 2008||Canadian fauna, 2008 Bibliobazar ed.|
|-Quebec||Present||Native||Not invasive||Provancher, 2008||Candian fauna, 2008, Bibliobazar ed.|
|Mexico||Localised||Introduced||Not invasive||Walne, 1956|
|USA||Present||Present based on regional distribution.|
|-Connecticut||Present||Native||Not invasive||Hoagland, 1985|
|-Delaware||Present||Native||Not invasive||Karlson and Shenk, 1983; Gaffney and McGee, 1992||Cap Henlopen|
|-Florida||Localised||Native||Not invasive||Frazier et al., 1985||Fixed on turtles|
|-Maine||Present||Native||Not invasive||Hoagland, 1985|
|-Massachusetts||Present||Native||Not invasive||Johnson, 1972; Hoagland, 1974; Hoagland, 1977; Hoagland, 1979||In Ipswich Bay and Cape Ann near Boston, in Buzzard Bay, in Vineyard Sound (Hoagland), in Woods Hole (Johnson)|
|-New Jersey||Present||Native||Not invasive||Bottom and Ropes, 1988||In Cap May|
|-New York||Present||Hoagland, 1985||Long Island Sound|
|-North Carolina||Present||Native||Not invasive||Hoagland, 1985|
|-Rhode Island||Present||Native||Not invasive||Hoagland, 1979; Pechenik and Lima, 1984||At Tiverton, on mussels (Hoagland) and Bissell Cowe (Pechenik)|
|-South Carolina||Present||Native||Not invasive||Hoagland, 1985|
|-Texas||Present||Walne, 1956; Tunnell and Chaney, 1970||On Texas just along coast|
|-Virginia||Present||Native||Not invasive||McGee and Targett, 1989||Atlas of Potomac river and of Chesapeake Bay|
|-Washington||Present||Introduced||Invasive||Hoagland, 1974; Hoagland, 1977||In the western USA it was imported with oysters in Puget Sound during the 1930s and is now common along the Washington state coastline|
|Uruguay||Present, few occurrences||Introduced||Not invasive||Walne, 1956||"some specimens were found on the Urugayan seaside"|
|Belgium||Widespread||Introduced||Invasive||Adam and Leloup, 1934; Polk, 1976||In Ostende Bay|
|Denmark||Present||Introduced||Sparck, 1949; Hessland, 1951||In the Limfjord|
|Finland||Present||Introduced||Leppäkoski and Olenin, 2000||Present in the list of alien species in the Baltic Sea|
|France||Widespread||Introduced||Invasive||Marteil, 1965; Blanchard, 1995; Montaudouin and Sauriau, 1999; Martin et al., 2006; Blanchard, 2009||From Belgium border to Arcachon Bay in Atlantic side and in Mediterranean lagoons|
|Germany||Widespread||Introduced||Invasive||Werner, 1949; Hessland, 1951; Thieltges et al., 2003; Thieltges et al., 2004||Wadden Sea, Sylt Islands|
|Greece||Present||Introduced||Not invasive||Galil and Zenetos, 2002||Individuals have been observed in Savonikos Bay, near the Peiraias Port, because of hull founling|
|Ireland||Last reported||1982||Introduced||1902||Not invasive||Arnold, 1960; Minchin and McGrath, 1995||First recorded in 1902, no record since 1982|
|Italy||Localised||Introduced||Not invasive||Natale ADi, 1982||On the northeastern coast of Sicily|
|Malta||Localised||Introduced||Not invasive||Cachia, 1981||Introduced with hull fouling, from Portugal|
|Netherlands||Widespread||Introduced||Invasive||Adam and Leloup, 1934; Nienhuis, 1992; Wolff, 2005||First live specimen found in 1926, today common in the Sheldt estuary, Zeeland, Calandkanaal, Beerkanaal and near Rotterdam basins (Wolff)|
|Norway||Present, few occurrences||Introduced||Invasive||Bergan, 1969; Bergstad, 1974; Hoisaeter, 1986; Sjotun, 1997||Several observed in Skagerrak. The extreme observation to the North is Kvitsoy, on the western coast|
|Spain||Widespread||Introduced||Invasive||Rolan, 1983; Rolan et al., 1985||In galician bays, under the oyster cultures|
|Sweden||Present||Introduced||Forsman, 1951; Hessland, 1951||Bohusland coast|
|UK||Widespread||Introduced||Invasive||Spencer, 1974; Utting and Spencer, 1992||Southern coasts of England and Wales|
|-Channel Islands||Widespread||Introduced||Invasive||Blanchard, 1995; Blanchard, 2009||Jersey and Guernsey|
History of Introduction and SpreadTop of page
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|Belgium||England and Wales||1911||Hitchhiker (pathway cause)||Yes||Polk (1962)|
|England and Wales||USA||1872||Hitchhiker (pathway cause)||Yes||Cole (1952); McMillan (1938)||The introduction of the slipper limpet in England is linked to oyster importation of Crassostrea virginica from the USA from the end of 19th century to the 1920s set on shores before being sold|
|Europe||USA||1970s||Hitchhiker (pathway cause)||Yes||Zibrowius (1991)||The introduction in Europe of Crassostrea gigas is known to be one of the main vector alien marine species|
|Europe||Japan||1970s||Hitchhiker (pathway cause)||Yes||Zibrowius (1991)||The introduction in Europe of Crossostrea gigas is known to be one of the main vector of alien marine species|
|France||1930s 1970s||Hitchhiker (pathway cause)||Yes||Blanchard (1995)||From England and Japan, in the 1930s with imports of farmed Ostrea edulis, during World War II and allied shipping operations in Normandy, and in the 1970s with import of Crassostrea gigas|
|Netherlands||England and Wales||1922||Hitchhiker (pathway cause)||Yes||Adam and Leloup (1934)||The transport of native oyster (Ostrea edulis)|
Risk of IntroductionTop of page
HabitatTop of page
Habitat ListTop of page
|Coastal areas||Principal habitat||Harmful (pest or invasive)|
|Coastal areas||Principal habitat||Natural|
|Mud flats||Secondary/tolerated habitat|
|Intertidal zone||Secondary/tolerated habitat|
|Inshore marine||Secondary/tolerated habitat|
|Benthic zone||Principal habitat||Natural|
Biology and EcologyTop of page
ClimateTop of page
|C - Temperate/Mesothermal climate||Preferred||Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C|
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Mean minimum temperature of coldest month (ºC)||5|
Water TolerancesTop of page
|Parameter||Minimum Value||Maximum Value||Typical Value||Status||Life Stage||Notes|
|Depth (m b.s.l.)||0-10||Optimum||Found up to 100 m in the Atlantic and intertidal areas|
|Dissolved oxygen (mg/l)||8-10||Optimum||5-10 tolerated; it can support low oxygen concentration and live in anaerobiose some hours|
|Salinity (part per thousand)||30||Optimum||20-40 tolerated; adult fecundity is not affected by low salinity (10 ppt)|
|Turbidity (JTU turbidity)||Optimum||0-10 g/l tolerated temporarily; the filtration rate is reduced at a minimum above 0.6 g/l. The quantity of pseudofaeces rises with suspension matter concentration, up to high levels|
|Velocity (cm/h)||Optimum||5 cm/s|
|Water temperature (ºC temperature)||15-20||Optimum||5-30 tolerated; the formation of egg capsules is triggered by temperatures of 10 and larvae appear above 10. High sensibility to cold temperatures|
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Asterias rubens||Predator||Adult||not specific|
|Cliona celata||Predator||Adult/Fry||not specific|
|Dicentrarchus labrax||Predator||Adult||not specific|
|Limanda limanda||Predator||Adult||not specific|
|Ocenebra erinacea||Predator||Adult/Fry||not specific|
|Pagurus pollicaris||Predator||Fry||not specific|
Notes on Natural EnemiesTop of page
Means of Movement and DispersalTop of page
Pathway CausesTop of page
|Aquaculture||Transported as a parasite of Ostrea edulis||Yes||Yes|
|Breeding and propagation||Yes|
|Fisheries||Dredging and trawling are a main cause of dispersion in western English Channel||Yes|
|Food||Introduced to England at the end of the 19th century to meet growing demand for oysters||Yes|
|Interbasin transfers||Regular practices of shellfish farmers.||Yes||Blanchard, 1995|
Pathway VectorsTop of page
|Aquaculture stock||From England to mainland countries during the 1930s||Yes||Blanchard, 1997|
|Containers and packaging - non-wood||During the 1970s from USA or Japan to Europe||Yes|
|Floating vegetation and debris||Evoqued for the introduction in Netherlands||Yes|
|Live seafood||From USA to England at the end of 19th century||Yes|
|Ship ballast water and sediment||A possibility for larvae||Yes|
|Ship hull fouling||For Italy or Greece (see history chapter), and for the arrival in Normandy in 1944||Yes||Blanchard, 1995|
|Soil, sand and gravel||It is one possibility between America and Europe||Yes|
|Water||The natural transport of mobile pelagic larva||Yes|
Impact SummaryTop of page
ImpactTop of page
Economic ImpactTop of page
The activities which have fallen victim to C. fornicata such as dredging or trawling, and shellfish-farming especially oysterfarming, are those which, for less than a hundred years, contributed, accidentally or not, to its spread. Dense limpet populations disturb fishery or oyster farming activities to such an extent that in some bays (Sheldt estuaries in Zeeland, Thames estuary and Fal River (Fitzgerald, 2007) in Great Britain, the Norman gulf or the Atlantic Marennes pond in France, cleaning operations are necessary. Regularly, oyster grounds must be cleaned before sowing new seed or when the C. fornicata populations create a too large negative effect. When limpets are fixed on oysters, oyster farmers must pick off limpets before selling the products, which creates an extra economic burden (Blanchard, 1997).
Expensive treatment methods have been developed, often without success. Public spending is constantly increasing. Yet applying the regulations or laws at the earliest observations would suffice to halt this spread. We are now observing in dense areas, the consequences of insufficient surveillance and precautions during the importation period.
Environmental ImpactTop of page
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Highly adaptable to different environments
- Is a habitat generalist
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Capable of securing and ingesting a wide range of food
- Benefits from human association (i.e. it is a human commensal)
- Long lived
- Fast growing
- Has high reproductive potential
- Has high genetic variability
- Altered trophic level
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Modification of natural benthic communities
- Negatively impacts cultural/traditional practices
- Negatively impacts aquaculture/fisheries
- Reduced native biodiversity
- Threat to/ loss of native species
- Competition - monopolizing resources
- Interaction with other invasive species
- Rapid growth
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
Uses ListTop of page
Animal feed, fodder, forage
- Fodder/animal feed
- Meat and bonemeal
- Soil improvement
- Research model
Human food and beverage
- Meat/fat/offal/blood/bone (whole, cut, fresh, frozen, canned, cured, processed or smoked)
Similarities to Other Species/ConditionsTop of page
Gaps in Knowledge/Research NeedsTop of page
ReferencesTop of page
Barnes RSK; Couglan J; Holmes J, 1973. A preliminary survey of the macroscopic bottom fauna of the Solent, with particular reference to Crepidula fornicata and Ostrea edulis. Proceedings of the Malacological Society of London, 40:253-275.
Blanchard M, 2009. Recent expansion of the slipper limpet population (Crepidula fornicata) in the Bay of Mont-Saint-Michel (Western Channel, France). Aquatic Living Resources, 22(1):11-19. http://www.alr-journal.org/index.php?option=article&access=standard&Itemid=129&url=/articles/alr/abs/2009/01/alr002-09/alr002-09.html
Blanchard M; Hamon D, 2006. [English title not available]. (Bilan du suivi de l'exploitation industrielle de la crépidule en Bretagne Nord (baies de Saint-Brieuc et du Mont Saint-Michel)) Rapport Ifremer dyneco/eb/06-01., 42 pp + annexes.
Blanchard M; Pechenik J; Giudicelli E; Connan JP; Robert R, 2008. Competition for food in the larvae of two marine molluscs Crepidula fornicata and Crassostrea gigas. Aquatic Living Resources, 21(2):197-205.
Bottom ML; Ropes JW, 1988. An indirect method for estimating longevity of the horseshoe crab (Limulus polyphemus) based on epifaunal slipper limpet Crepidula fornicata. Journal of Shellfish Research, 7(3):407-712.
Decottignies P; Beninger P; Rincé Y; Riera P, 2007. Trophic interactions between two introduced suspension-feeders, Crepidula fornicata and Crassostrea gigas, influenced by seasonal effects and qualitative selection capacity. J. Exp. Mar. Biol. Ecol, 342(2):231-241.
Decottignies P; Beninger P; Rincé Y; Robins RJ; Riera P, 2007. Exploitation of natural food sources by two sympatric invasive suspension-feeders Crassostrea gigas and Crepidula fornicata. Marine Ecology Progress Series, 334:179-192.
Dupont L; Richard J; Paulet YM; Thouzeau G; Viard F, 2006. Gregariousness and protandry promote reproductive insurance in the invasive gastropod Crepidula fornicata; evidence for assignment of larval paternity. Molecular Ecology, 15(10):3009-3021.
Ehrhold A; Blanchard M; Auffret JP; Garlan T, 1998. [English title not available]. (Conséquences de la prolifération de la crépidule (Crepidula fornicata) sur l'évolution sédimentaire de la baie du Mont Saint-Michel (Manche-Ouest)) C. R. Acad. Sci. Paris - Sciences de la terre, 327:583-588.
Ehrhold A; Blanchard M; Auffret JP; Garlan T, 1998. [English title not available]. (Conséquences de la prolifération de la crépidule (Crepidula fornicata) sur l'évolution sédimentaire de la baie du Mont Saint-Michel) Compte Rendu Acad. Sciences,Sciences de la terre, 327:583-587.
Galil BS; Zenetos A, 2002. A sea change - Exotics in the eastern Mediterranean Sea. In: Invasive species of Europe; distribution, impact and management [ed. by Leppäkoski E, Gollasch S, Olenin] Dordrecht, The Netherlands: Kluwer Academic Publishers, 325-326.
Hamon D; Blanchard M; Houlgatte E; Blanchet A; Gaffet D; Cugier P; Ménesguen A; Cann P; Domalain D; Hautbois AG, 2002. Programme Liteau: la crépidule; identifier les mécanismes de sa prolifération et caractériser ses effets sur le milieu pour envisager sa gestion. Chantier Baie de St Brieuc. Rapport final Liteau. Rapport Ifremer/del.ec, Plouzané-France., 70 pp.
Martin S; Thouzeau G; Chauvaud L; Jean F; Guerin L; Clavier J, 2006. Respiration, calcification and excretion of the invasive C. fornicata Crepidula fornicata L.; implication for carbon, carbonate and nitrogen fluxes in affected areas. Limnology and Oceanography, 51(5):1996-2007.
Pape OLe; Guérault D; Désaunay Y, 2004. Effect of an invasive mollusc, American slipper limpet Crepidula fornicata, on habitat suitability for juvenile common sole Solea solea in the Bay of Biscay. Marine Ecology Progress Series, 277:107-115.
Pechenik JA; Jarrett JN; Rooney J, 2002. Relationships between larval nutritional experience, larval growth rates, juvenile growth rates, and juvenile feeding rates in the prosobranch gastropod Crepidula fornicata. J. Exp. Mar. Biol. Ecol, 280(1-2):63-78.
Thieltges DW; Strasser M; Beusekom JEEvan; Reise K, 2004. Too cold to prosper - winter mortality prevents population increase of the introduced American slipper limpet Crepidula fornicata in northern Europe. Journal of Experimental Marine Biology and Ecology, 311(2):375-391.
OrganizationsTop of page
France: French Institute for Marine Research, Technopole Brest, 29280 Plouzane, http://www.ifremer.fr
ContributorsTop of page
21/05/09 Original text by:
Michel Blanchard, laboratoire Benthos, département DYNECO, IFREMER, BP 70 - 29280 PLOUZANE, France
Distribution MapsTop of page
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