BIOTIC Species Information for Crepidula fornicata
Researched byWill Rayment Data supplied byMarLIN
Refereed byDr Frédérique Viard
Scientific nameCrepidula fornicata Common nameSlipper limpet
MCS CodeW439 Recent SynonymsNone

PhylumMollusca Subphylum
Superclass ClassGastropoda
SubclassProsobranchia OrderMesogastropoda
Suborder FamilyCalyptraeidae
GenusCrepidula Speciesfornicata

Additional InformationCrepidula fornicata is a non-native species. The modern British population is known to have been introduced to Essex between 1887 and 1890 in association with oysters, Crassostrea virginica, imported from North America (Fretter & Graham, 1981; Eno et al., 1997).
Taxonomy References Fretter & Graham, 1981, Howson & Picton, 1997, Hayward et al.., 1996, Fish & Fish, 1996, Hayward & Ryland, 1995b, Eno et al., 1997,
General Biology
Growth formTurbinate
Feeding methodActive suspension feeder
Permanent attachment
Environmental positionEpibenthic
Typical food typesPhytoplankton and particulate organic food HabitAttached
Bioturbator FlexibilityNone (< 10 degrees)
FragilityRobust SizeSmall-medium(3-10cm)
HeightInsufficient information Growth Rate0.04-1.11 mm/day
Adult dispersal potential10-100m DependencyIndependent
General Biology Additional InformationAbundance
In the Bay of Marennes-Oleron, France, Crepidula fornicata was found in a wide range of sediment grain sizes and depths. Maximum abundance and biomass reached 4770 individuals per m² and 354 g of dry weight per m² respectively in shallow muddy areas (De Montaudouin & Sauriau, 1999). Crepidula fornicata also occurs at "moderate" density, for example in the Arcachon Basin (De Montaudouin et al., 2001).

Size at maturity
Due to the protandrous hermaphroditic life-cycle of Crepidula fornicata, size at maturity is difficult to ascertain. Warne(1956), cited in Fretter & Graham (1981), reported size at maturity to be 4 mm but it is unclear whether this referred to both sexes or males only. Under laboratory conditions, Nelson et al. (1983) reported that the mean female length at first larval release was 23.8 mm.

Growth rate
Reported growth rates vary according to age. Pechenik et al. (1996) recorded juvenile growth rate for the 9 days after metamorphosis as varying between 15-225µm per day (mean 110.5µm per day). Thouzeau(1991) recorded mean juvenile growth rates over 1 month following settlement as 38-48µm per day with a maximum of 90µm per day.

Immediately after settlement, juvenile Crepidula fornicata are capable of slow crawling and locate a suitable site for attachment and growth. This is either a stone or a chain of other Crepidula fornicata (conspecifics). The shell then grows to fit the substratum and consequently most animals are incapable of further movement at the age of about 2 years (Fretter & Graham, 1981).

Following laboratory experiments, Thain (1984) deduced that, for optimum growth and reproduction, an individual Crepidula fornicata being fed with the alga Phaeodactylum tricornutum requires 5 x 108 algal cells per gram of flesh wet weight per day.
Biology References Fretter & Graham, 1981, Hayward et al.., 1996, Montaudouin de & Sauriau, 1999, Nelson et al., 1983, Pechenik et al., 1996, Thouzeau, 1991, Thain, 1984, Blanchard, 1997, Sauriau et al., 1998, Ehrhold et al., 1998, Montaudouin de et al., 2001,
Distribution and Habitat
Distribution in Britain & IrelandIn Britain, it is present on the east coast south of Spurn Head, the length of the south coast and northwards along the west coast to Cardigan Bay. It has been introduced accidentally to several locations in Ireland but a population has never persisted.
Global distributionOriginally found on the east coast of the Americas between Canada and Mexico. Now also introduced to British-Columbia, Washington state, Japan and Europe, where it is found on the Atlantic coast between Denmark and Spain, in Sicily and the Adriatic Sea.
Biogeographic rangeNot researched Depth rangeLow water mark to 60 m
MigratoryNon-migratory / Resident   
Distribution Additional InformationAlthough Crepidula fornicata is a cosmopolitan species, which can tolerate a wide range of environmental conditions, populations are particularly well developed in wave protected areas such as bays, estuaries or sheltered sides of wave exposed islands (Blanchard, 1997). Similarly, the species is found on a variety of substrata but is most abundant in muddy or mixed muddy areas (De Montaudouin & Sauriau, 1999).

Substratum preferencesSmall boulders
Muddy gravel
Gravel / shingle
Fine clean sand
Coarse clean sand
Muddy sand
Sandy mud
Other species (see additional information)
Physiographic preferencesOpen coast
Strait / sound
Enclosed coast / Embayment
Biological zoneSublittoral Fringe
Upper Infralittoral
Lower Infralittoral
Upper Circalittoral
Lower Circalittoral
Wave exposureSheltered
Very Sheltered
Extremely Sheltered
Tidal stream strength/Water flowModerately Strong (1-3 kn)
Weak (<1 kn)
Very Weak (negligible)
SalinityVariable (18-40 psu)
Habitat Preferences Additional Information
Distribution References Fretter & Graham, 1981, Hayward et al.., 1996, Fish & Fish, 1996, Montaudouin de & Sauriau, 1999, Minchin et al., 1995, Barnes et al., 1973, Blanchard, 1997, Connor et al., 1997(a), JNCC, 1999,
Reproduction/Life History
Reproductive typeProtandrous hermaphrodite
Developmental mechanismPlanktotrophic
Reproductive SeasonFebruary to October Reproductive LocationInsufficient information
Reproductive frequencyAnnual protracted Regeneration potential No
Life span6-10 years Age at reproductive maturity<1 year
Generation time1-2 years FecundityCa 4000 larvae
Egg/propagule size Fertilization typeInsufficient information
Larval/Juvenile dispersal potential>10km Larval settlement periodInsufficient information
Duration of larval stage1-2 months   
Reproduction Preferences Additional InformationGeneral
Crepidula fornicata is a protandrous hermaphrodite. This means that the animals start their lives as males and then subsequently may change sex and develop into females. Although breeding can occur between February and October, peak activity occurs in May and June when 80-90% of females spawn. Most females spawn twice in a year, apparently after neap tides. The spat settle in isolation or on top of an established chain. If the individual settles alone, it becomes male briefly, passing rapidly on to a female, especially if another animal settles on it to initiate chain formation. Sex change can only occur to the bottom-most male in a stack and takes approximately 60 days, during which the penis regresses and the pouches and glands of the female duct develop. If a juvenile settles on an established stack it develops and may remain as a male for an extended period (up to 6 years), apparently maintained by pheromones released by females lower in the stack (Fretter & Graham, 1981).

Age at maturity
Due to the protandrous hermaphroditic lifecycle of Crepidula fornicata, age at maturity is difficult to ascertain. Warne(1956), cited in Fretter & Graham (1981), reported size at maturity to be 4mm but it is unclear whether this refers to both sexes or males only. A size of 4mm would be achieved approximately 2 months after settlement. Under laboratory conditions, Nelson et al.(1983) report that the mean time from being spawned to first larval release for females was 300 days, i.e.. maturity is reached approximately 10 months after settlement.

Generation time
Generation time is complicated by the hermaphroditic life-cycle of Crepidula fornicata. Incubation of the eggs takes 2-4 weeks and the duration of the larval phase is 4-5 weeks (Fretter & Graham, 1981; Thouzeau, 1991). Using the ages at maturity quoted above, it would appear that males are capable of breeding as little as 4 months after fertilization. Under laboratory conditions, Nelson et al. (1983) reported the female generation time to be 300 days. However, in situ females were not reported to spawn until their third year (Deslou-Paoli & Heral, 1986).

Females can lay around 11000 eggs at a time contained in up to 50 egg capsules (Deslou-Paoli & Heral, 1986). Laboratory experiments by Thain (1984) revealed that following incubation, approximately 4000 larvae were released per female.
Reproduction References Fretter & Graham, 1981, Fish & Fish, 1996, Nelson et al., 1983, Thain, 1984, Deslou-Paoli & Heral, 1986, Montaudouin de et al., 2001,
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