Crepidula cachimilla, copyright Andrea Talone Rio.

Belongs within: Calyptraeidae.
Contains: Crepidula (Crepidula).

Slippers on the coast
Published 5 August 2019

The ‘limpet’ form is something that has evolved numerous times among gastropods, as various lineages of marine snail converted to a more or less unwhorled shell and low profile. In many cases, the evolution of the limpet form is also associated with high energy environments, the ability to nestle against rocks helping the gastropod maintain its grip against the surge of the waves. In the modern world, the most diverse and familiar lineage of limpets is that including the common limpets of the genus Patella and their relatives, but there also many independent lineages to be found. One of these is the slipper limpets of the genus Crepidula.

Various views of shell of Crepidula onyx, copyright H. Zell.

Slipper limpets get their vernacular name from the shape of their shell, whose more or less oval shape together with a jutting internal horizontal shelf (the septum) at one end gives the overall impression of a carpet slipper. About forty species (including fossils) of Crepidula are currently recognised worldwide. Species recognition has historically been difficult owing to their simple form and tendency to vary according to the environment in which they mature, but Hoagland (1977) identified a number of key distinguishing features such as disposition and shape of the muscle scars, features of the septum, and conformation of the apical beak of the shell. In contrast to the grazing common limpets, slipper limpets are filter feeders using their gill to capture micro-algae from the water column. They are protandric hermaphrodites, beginning their life as males but maturing into females as they grow. Eggs are brooded under the shell when first produced; in some species, the eggs are subsequently released to hatch into planktonic larvae whereas other species produce fewer eggs but retain them until the young have developed to the crawling stage. For instance, two species found on the east coast of North America that are very similar in adult appearance and have been confused historically differ in that Crepidula ustulatulina, found around Florida and the Gulf of Mexico, produces free-living larvae whereas the more northerly C. convexa does not.

Mating stack of Crepidula fornicata, copyright Dendroica cerulea.

The most renowned species of slipper limpet is the northern Atlantic Crepidula fornicata. This species was originally native to the eastern coast of North America but was accidentally imported to Europe in the late 1800s in association with oysters being transported as stock for farming (Blanchard 1997). In the subsequent years, C. fornicata has become increasingly widespread on the shores of Europe, and is often a significant fouling pest for oyster farms. It has also been introduced to even further flung locations such as Japan and Washington State. Crepidula fornicata is famed for its habit of forming high mating stacks with several smaller males living permanently on the dorsal surface of larger females. If the female of a stack dies, the largest male may develop into a female. Not all Crepidula species form such stacks: in some, just two or three individuals may form a temporary cluster when mating.

Historically, Crepidula has been distinguished from other genera in the limpet family Calyptraeidae by their posterior shell apex and flat septum (other calyptraeid genera may have a cone-shaped shell and/or cup-shaped septum). However, a molecular analysis of the family by Collin (2003) found that species of Crepidula sensu Hoagland (1977) did not form a single clade within Calyptraeidae, and the genus’ prior members are now divided between at least four genera. While these genera may be distinguishable using features of the soft anatomy, they are almost indistinguishable from the shells alone.

Systematics of Crepidula
<==Crepidula Lamarck 1799HP04 [=Crypta Gray 1847 non Stephens 1830F27a, BR05; Cryptaina]
    |--C. cachimilla Cledón, Simone & Penchaszadeh 2004S11
    `--+--C. argentina Simone, Pastorino & Penchaszadeh 2000S11
       `--+--C. (Crepidula)S11
          `--+--C. carioca Simone 2006S11
             `--C. pyguaia Simone 2006S11
Crepidula incertae sedis:
  C. arenataC64
  C. barbudaensis Usticke 1969BC01
  ‘Crypta’ contortaH79
  ‘Crypta’ costataH79
  C. derjugini Golikov & Kussakin 1962V89
  C. dilatataCF02
  C. excavataC64
  C. fecunda Gallardo 1979CF02
  C. gregaria [incl. Haliotis imperforata Philippi 1887 non Gmelin 1791]F27b
  C. incurva (Broderip 1834)V89 [=Crypta incurvaH79]
  C. incurvata Broderip & Sowerby 1829BS29
  C. lessonii (Broderip 1834)V89
  C. lirataC64
  C. maculosa Conrad 1846HP04
  C. marginalisC64
  C. monoxylaHS01
  C. navicelloides [=Scutellina navicelloides; incl. C. explanata, C. minuta]C64
  C. perforans (Valenciennes 1846)V89
  C. philippianaCF02
  C. porcellanaG79
  C. princeps [incl. C. prorupta]C64
  C. profundaHS01 [=Crypta profundaH79]
  C. rugosa Nutt. 1856C64
  C. squamaC64
  C. striolata (Menke 1851)V89
  C. uncata [incl. C. rostrata]C64
  C. unguiformisH86
  C. (Crepipatella Lesson 1830)O27
    `--C. (C.) lingulata (Gould 1846)O27 (see below for synonymy)
  C. (Ianacus Morch 1852)O27
    |--C. (I.) fimbriata Reeve 1859O27
    |--C. (I.) nivea Adams 1852O27
    |    |--C. n. niveaO27
    |    `--C. n. glottidiarum Dall 1905O27
    `--C. (I.) nummaria Gould 1846O27
  C. (Siphopatella) walshi (Reeve 1859)V89
Nomen nudum: Crepidula nautiloidesC64

Crepidula (Crepipatella) lingulata (Gould 1846)O27 [=C. dorsata var. lingulataC64; incl. C. dorsata var. bilobataC64, C. dorsataC64]

*Type species of generic name indicated


Blanchard, M. 1997. Spread of the slipper limpet Crepidula fornicata (L. 1758) in Europe. Current state and consequences. Scientia Marina 61 (Suppl. 2): 109–118.

[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1-2): 1-397.

[BC01] Boyko, C. B., & J. R. Cordeiro. 2001. Catalog of Recent type specimens in the Division of Invertebrate Zoology, American Museum of Natural History. V. Mollusca, part 2 (class Gastropoda [exclusive of Opisthobranchia and Pulmonata], with supplements to Gastropoda [Opisthobranchia], and Bivalvia). Bulletin of the American Museum of Natural History 262: 1–170.

[BS29] Broderip, W. J., & G. B. Sowerby. 1829. Observations on new or interesting Mollusca contained, for the most part, in the Museum of the Zoological Society. Zoological Journal 4: 359–379, pl. 9.

[C64] Carpenter, P. P. 1864. Supplementary report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. Report of the British Association for the Advancement of Science 33: 517–686.

[CF02] Chaparro, O. R., & M. L. Flores. 2002. Reproductive output of Crepidula fecunda females: Distribution of energy in the production of gametes and capsular walls. New Zealand Journal of Marine and Freshwater Research 36: 661–673.

Collin, R. 2003. Phylogenetic relationship among calyptraeid gastropods and their implications for the biogeography of marine speciation. Systematic Biology 52 (5): 618–640.

[F27a] Finlay, H. J. 1927a. A further commentary on New Zealand molluscan systematics. Transactions and Proceedings of the New Zealand Institute 57: 320–485.

[F27b] Finlay, H. J. 1927b. New specific names for austral Mollusca. Transactions and Proceedings of the New Zealand Institute 57: 488–533.

[G79] Guppy, R. J. L. 1879. First sketch of a marine invertebrate fauna of the Gulf of Paria and its neighbourhood. Part I.—Mollusca. Journal of Conchology 2: 151–172.

[H79] Haast, J. von. 1879. Geology of the Provinces of Canterbury and Westland, New Zealand. A report comprising the results of official explorations. “Times” Office: Christchurch.

[HS01] Hayward, B. W., A. B. Stephenson, M. S. Morley, W. M. Blom, H. R. Grenfell, F. J. Brook, J. L. Riley, F. Thompson & J. J. Hayward. 2001. Marine biota of Parengarenga Harbour, Northland, New Zealand. Records of the Auckland Museum 37: 45–80.

[HP04] Herbert, G. S., & R. W. Portell. 2004. First paleontological record of larval brooding in the calyptraeid gastropod genus Crepidula Lamarck, 1799. Journal of Paleontology 78 (2): 424–429.

Hoagland, K. E. 1977. Systematic review of fossil and recent Crepidula and discussion of evolution of the Calyptraeidae. Malacologia 16 (2): 353–420.

[H86] Hutton, F. W. 1886. The Mollusca of the Pareora and Oamaru systems of New Zealand. Proceedings of the Linnean Society of New South Wales, series 2, 1 (1): 205–237.

[O27] Oldroyd, I. S. 1927. The Marine Shells of the West Coast of North America vol. 2 pt 3. Stanford University Press: Stanford University (California).

[S11] Simone, L. R. L. 2011. Phylogeny of the Caenogastropoda (Mollusca), based on comparative morphology. Arquivos de Zoologia 42 (4): 161–323.

[V89] Vermeij, G. J. 1989. Habitat and form of Crepidula grandis in Japan, with comments on habitat specialization in calyptraeid gastropods. Nautilus 103 (3): 89–91.

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