slipper shells

  Crepidula fornicata
(Linnaeus, 1758)

Relevant Synonyms


 photo: S. Gofas / Coll. J. Pelorce    

Shell moderately convex, ovate, rather thin, with apex at posterior margin, slighly curled dextrally. Outer surface smooth or with only growth lines. Inside with a septum which occupies the posterior half. Edge of shell thin and cutting.

color : exterior with pale purplish or brownish stains on a dirty grey background; inside with a similar but vivid pattern of purplish blotches, and white septum.

common size : up to 50 mm in the Atlantic, Mediterranean specimens smaller.

This species is distinguished from the native species by being definitely convex and growing much larger, and by the mottled color pattern; from the West African C. porcellana (Linnaeus, 1758) by its larger size and profile which is evenly rounded, not subcarinate.

Individuals of Crepidula fornicata pile up on each other, the older specimens being females and the younger (on top), males which will eventually turn into females as the pile grows. The biology of this species has been studied in detail by Le Gall (1980).

habitat : on sand or gravel bottoms in low energy environments, in which the accumulation of shells may lead to the formation of a biogenic hard substrate.

1st Mediterranean record
La Seyne-sur-mer, France, 1992 [1957].

Worldwide: Atlantic coast of America, from Canada to Texas; introductions have accompanied oyster farming in NW Europe, where it has become invasive; also Pacific coast of the United States. Mediterranean: record mostly limited to lagoons where marine farming is active; France : collected first in 1957 La Seyne-sur-mer, (Zibrowius, 1992), Salses-Leucate (Clanzig, 1989), Thau (Zibrowius, pers. comm.); Malta: Marsamxett harbour and Marsaxlokk Bay (Cachia, 1981); Italy: lagoon of Faro, Sicily (Di Natale, 1982) and Caprolacce Lagoon (Bini, 1983); Greece: Saronikos Gulf, Evvoikos (Delamotte and Vardala-Theodorou, 1994). On the French coast, the species is occasionally found offshore, in the Rhone delta area.

Always rare in the Mediterranean.

speculated reasons for success :

With oyster farming, presumably through separate introductions from the French Atlantic coast to the French Mediterranean lagoons, and from unknown origin to the Italian and Maltese sites. The Saronikos Gulf record (near Peiraias port) may be attributed to shipping as there is no oyster farming nearby.

A serious pest due to large-scale proliferation on oyster-farming or fishing grounds in the Atlantic. In the Mediterranean, the species is too sporadic to be of importance.


  • Clanzig S., 1989. Introduction récente d'invertébrés dans les lagunes Mediterranéennes du Languedoc-Roussilon (France). Bulletin de la Societe Zoologique de France, 114(3): 151-152.
  • Le Gall P., 1980. Etude expérimentale de l'association en chaîne et de son influence sur la croissance et la sexualité chez la crépidule Crepidula fornicata Linnaeus, 1758 (Mollusque mésogastéropode). Doctoral Thesis, University of Caen.
  • Minchin D., McGrath D. and 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(3): 249-256.


  • Zibrowius H., 1992. Ongoing modifications of the Mediterranean marine fauna and flora by the establishment of exotic species. Mésogée, 51: 83-107.


Last update : December 2003

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