The Entoprocta are a small phylum of minute, solitary or colonial, sessile, aquatic animals. Approximately 200 species have been described worldwide, with only 1 species occurring in freshwater. The colonial species encrust stones, shells and algae. The solitary species are almost always less than one millimetre long; the individuals in the colonial species may reach several millimetres. Each individual consists of a globular body with a crown of tentacles around a concave, ventral area and a cylindrical stalk. The ciliated tentacles create a water current between the tentacles and away from the mouth. Food particles are captured from this current by compound cilia on the lateral sides of the tentacles. The solitary species are mostly associated with water‐current‐producing hosts, such as polychaetes, sponges and bryozoans; these species are not conspicuous and most of the reported distributions reflect specialists’ searches. Development is indirect with more or less typical trochophora larvae.

Key Concepts:

  • Entoprocts are small solitary or colonial aquatic organisms.

  • The colonial species grow on stones, shells or algae, whereas most of the solitary species are associated with other marine invertebrates, especially polychaetes and sponges.

  • Entoprocts are filter feeders that capture plankton particles with compound cilia on a horseshoe of tentacles.

  • Sexual reproduction is through spiral cleavage and trochophora larvae, which either settle and go through a metamorphosis or develop buds which detach from the larval body.

  • Asexual reproduction is through budding from the frontal side of the body in the solitary species and through budding from stolons or a basal plate in the colonial species.

Keywords: budding; cleavage; colonies; filter feeding; larvae; trochophore

Figure 1.

Part of a colony of Pedicellina cernua. The white structures are embryos/larvae in the atrium. Photo courtesy of M. Faasse, www.acteon.nl. © M. Faasse.

Figure 2.

A solitary (Loxosomella) and a colonial (Pedicellina) entoproct. Modified from Nielsen and Jespersen . Reprinted by permission of Wiley‐Liss Inc.



Edgecombe G, Giribet G, Dunn C et al. (2011) Higher‐level metazoan relationships: recent progress and remaining questions. Organisms Diversity and Evolution 11: 151–172.

Nielsen C (1971) Entoproct life‐cycles and the entoproct/ectoproct relationship. Ophelia 9: 209–341.

Nielsen C and Jespersen Å (1997) Entoprocta. In: Harrison FW (ed.) Microscopic Anatomy of Invertebrates, vol. 13, pp. 13–43. New York: Wiley‐Liss.

Riisgård HU, Nielsen C and Larsen PS (2000) Downstream collecting in ciliary suspension feeders: the catch‐up principle. Marine Ecology Progress Series 207: 33–51.

Todd JA and Taylor PD (1992) The first fossil entoproct. Naturwissenschaften 79: 311–314.

Further Reading

Brusca RC and Brusca GJ (2003) Invertebrates, 2nd edn. Sunderland, MA: Sinauer Associates.

Nielsen C (1989) Entoprocts. Synopses of the British Fauna (New Series) no. 41. Leiden, The Netherlands: Brill.

Nielsen C (2012) Animal Evolution: Interrelationships of the Living Phyla, 3rd edn. Oxford: Oxford University Press.

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Nielsen, Claus(May 2013) Entoprocta. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001596.pub2]