Crepidula fornicata

Phylum: Mollusca
Class: Gastropoda
Order: Mesogastropoda
Species name: Crepidula fornicata (Linnaeus 1758)
Synonyms: None
Common name: Slipper limpet
Date of introduction and origin
The first known occurrence of Crepidula fornicata in Europe was in 1872 in Liverpool Bay, but populations in this area have since died out. Crepidula fornicata is known to have been introduced to Essex between 1887 and 1890 from North America (Loosanoff 1955; Crouch 1894, 1895; Orton 1912; Fretter & Graham 1981).
Method of introduction
The individuals in Essex from which the spread of Crepidula started were introduced in association with imported American oysters Crassostrea virginica. This species may also be transported on ships' hulls (Franklin & Pickett 1974), and in ballast water in the pelagic larval phase. Historic populations (now extinct) have also been introduced in association with the American hard shelled clam Mercenaria mercenaria (McMillan 1938; Minchin McGrath & Duggan 1995).
Reasons for success
Its success is probably due to a lack of predators and the unusual method of reproduction (which relies upon individuals settling upon each other and reproduction thus being assited through their close proximity); and a pelagic larval stage aids the spread once introduced.
Rate of spread and methods involved
It showed fairly rapid spread (Franklin & Pickett 1974), from Essex to Weymouth, Dorset by 1945 (Seaward 1987), and by the early 1950s its range had extended to Northumberland (see Minchin, McGrath & Duggan 1995).
This species is found in southwest, south and southeast Britain and as far north as Pembrokeshire on the west coast and Yorkshire on the east coast (Hancock 1969; Utting & Spencer 1992; Spencer 1990; Smith 1995; Chipperfield 1951). It does not occur in any abundance deeper than 30 metres (Barnes, Coughlan & Holmes 1973). It also occurs off mainland Europe, as far north as southern Norway on the Skagerak coast.
Factors likely to influence spread and distribution
Minimum winter temperatures may be important in limiting the ability to develop extensive populations in the north of Britain (Minchin, McGrath & Duggan 1995).
Effects on the environment
It competes with other filter-feeding invertebrates for food and space, and in waters of high concentrations of suspended material it encourages deposition of mud owing to the accumulation of faeces and pseudofaeces (Barnes, Coughlan & Holmes 1973).
Effects on commercial interests
It is considered a pest on commercial oyster beds, competing for space and food, while depositing mud on them (Utting & Spencer 1992) and the mud rendering the substratum unsuitable for the settlement of spat (Barnes, Coughlan & Holmes 1973). In parts of Essex slipper limpets were said to far exceed oysters in abundance (Walne 1956).
Control methods used and effectiveness
Dipping infested culch and oysters in saturated solutions of brine for a short period (Hancock 1969; Franklin 1974) is the cheapest, safest and most effective method of control. For clearance of large beds, dredging and disposal above high water mark has been applied (Hancock 1969).
Beneficial effects
It has been suggested that the shells may be used as oyster culch for spatfalls in the Solent (Barnes, Coughlan & Holmes 1973).
It is thought to have been introduced to France with oysters from England. It has attained dense concentrations of up to 1750 m-2 and in some areas has been the dominant member of the macrofauna (Seaward 1987).
Barnes, R.S.K., Coughlan, J., & Holmes, N.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, 40: 253-275.
Chipperfield, P.N.J. 1951. The breeding of Crepidula fornicata in the River Blackwater, Essex. Journal of the Marine Biological Association of the United Kingdom, 30: 49-71.
Crouch, W. 1894. On the occurrence of Crepidula fornicata (L.) off the coast of Essex. Essex Naturalist, 8: 36-38.
Crouch, W. 1895. On the occurrence of Crepidula fornicata in Essex. Proceedings of the Malacological Society, 1: 19.
Franklin, A. 1974. The destruction of the oyster pest Crepidula fornicata by brine-dipping. Fisheries Laboratory, Ministry of Agriculture Fisheries and Food, Lowestoft. (Technical Report No 8).
Franklin, A., & Pickett, G.D. 1974. Recent research on introduced oyster pests in England and Wales. Unpublished, International Council for the Exploration of the Sea. (Paper, No. CM 1974/K:15.)
Fretter, V., & Graham, A. 1981. The prosobranch molluscs of Britain and Denmark, part 6. Journal of Molluscan Studies, supplement 9, 285-363.
Hancock, D.A. 1969. Oyster pests and their control. Burnham on Crouch, Ministry of Agriculture Fisheries and Food. (Laboratory Leaflet (New Series), No. 19.)
Hayward, P.J., & Ryland, J.S. eds. 1990. The marine fauna of the British Isles and north-west Europe. 2 vols. Oxford, Clarendon Press.
Loosanoff, V.L. 1955. The European oyster in American waters. Science,121 (3135): 110-121.
McMillan, N.F. 1938. Early records of Crepidula in English waters. Proceedings of the Malacological Society, 23: 236.
Minchin, D., McGrath, D., & Duggan, C.B. 1995. The slipper limpet, Crepidula fornicata (L.), in Irish waters, with a review of its occurrence in the north-eastern Atlantic. Journal of Conchology, 35: 247-254.
Orton, J.H. 1912. An account of the natural history of the slipper-limpet (Crepidula fornicata), with some remarks on its occurrence on the oyster grounds of the Essex coast. Journal of the Marine Biological Association of the United Kingdom, 9: 437-443.
Seaward, D.R. 1987. The marine molluscs of Portland Harbour, Dorset. Proceedings of the Dorset Natural History and Archaeological Society, 108: 159-167.
Smith, S. 1995. Crepidula fornicata (L., 1758) (Mollusca: Gastropoda) at Tenby, south west Wales. Porcupine Newsletter, 6: 82.
Spencer, B.E. 1990. Cultivation of Pacific oysters. Lowestoft, Ministry of Agriculture, Fisheries and Food. (Laboratory Leaflet No. 63).
Utting, S.D., & Spencer, B.E. 1992. Introductions of marine bivalve molluscs into the United Kingdom for commercial culture - case histories. ICES Marine Science Symposium, 194: 84-91.
Walne, P.R. 1956. The biology and distribution of Crepidula fornicata in Essex rivers. Ministry of Agriculture, Fisheries and Food, Fisheries Investigations II, Series XX, No. 6: 1-50.