A coelomate animal is basically a set of concentric tubes, with a gap between the gut and the outer tubes.

The coelom (play /ˈsləm/ see-ləm) (also celom) is a fluid-filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsequently lost in several lineages. Loss of coelom is correlated with reduction in body size. Coeloms are only ever present in triploblastic animals, though coelom is sometimes (incorrectly) used to refer to any developed digestive tract.

Functionally, a coelom can absorb shock or provide a hydrostatic skeleton. It also allows organs to grow independently off the body wall. This can be seen in the digestive tract of earthworms and other annelids, which is suspended within the body in a mesentery derived from a mesoderm-lined coelom. In mammals, the coelom forms the peritoneal, pleural, and pericardial cavities.

In the past, zoologists grouped animals based on characters related to the coelom. The presence or absence of a coelom and the way in which it was formed was believed to be important in understanding the phylogenetic relationships of animal phyla. However, recent molecular phylogenies have suggested this characteristic is not as informative as previously believed: the coelom may have arisen twice, once in protostomes and once among the deuterostomes.[1] The coelomate phyla comprise Entoprocta, Ectoprocta, Phoronida, Brachiopoda, Mollusca, Priapulida, Sipuncula, Echiura, Annelida, Tardigrada, Pentastoma, Onychophora, Arthropoda, Pogonophora, Echinodermata, Chaetognatha, Hemichordata and Chordata.[2]

See also


  1. ^ Xiao, S.; Laflamme, M. (2008). "On the eve of animal radiation: phylogeny, ecology and evolution of the Ediacara biota". Trends in Ecology & Evolution 24 (1): 31–40. doi:10.1016/j.tree.2008.07.015. PMID 18952316 
  2. ^ "Coeloms and Pseudocoeloms". Retrieved August 30, 2011. 

Further reading

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  • Coelom — Coelom, sekundäre Leibeshöhle, von Mesoderm Epithel ausgekleideter Hohlraum, der bei höheren Tieren (⇒ Bilateria) die ursprüngliche primäre Leibeshöhle (Blastocoel) verdrängt …   Deutsch wörterbuch der biologie

  • coelom — [sē′ləm] n. [Gr koiloma < koilos: see COELE] the main body cavity of most higher multicellular animals, in which the visceral organs are suspended coelomic [si läm′ik, silō′mik] adj …   English World dictionary

  • Coelom — Mit Zölom (griech coiloma Vertiefung, Hohlraum) bezeichnet man die sekundäre Leibeshöhle zahlreicher Tiere, etwa der Chordatiere oder der Ringelwürmer. Es handelt sich dabei um einen flüssigkeitsgefüllten Hohlraum, der von einem mesodermalen… …   Deutsch Wikipedia

  • coelom — noun (plural coeloms or coelomata) Etymology: German, from Greek koilōma cavity, from koilos Date: 1875 the usually epithelium lined space between the body wall and the digestive tract of metazoans above the lower worms • coelomate adjective or… …   New Collegiate Dictionary

  • coelom — the fluid filled abdominal cavity or body cavity containing the guts, gonads, kidneys, etc …   Dictionary of ichthyology

  • coelom — n. [Gr. koilos, hollow] The body cavity or space between the body wall and internal organs lined with mesoderm in many metazoan animals …   Dictionary of invertebrate zoology

  • coelom — Body cavity characteristic of most multicellullular animals (all coelomates). Arises within the embryonic mesoderm, that is thereby subdivided into somatic mesoderm and splanchnic mesoderm, and is lined by the mesodermally derived peritoneum. May …   Dictionary of molecular biology

  • coelom — coelomic /si lom ik, loh mik/, adj. /see leuhm/, n., pl. coeloms, coelomata /si loh meuh teuh/. Zool. the body cavity of higher metazoans, between the body wall and intestine, lined with a mesodermal epithelium. Also, coelome /see lohm/, celom.… …   Universalium

  • coelom — noun A fluid filled cavity within the body of an animal. The digestive system is suspended within the cavity, which is lined by a tissue called the peritoneum. See Also: coelomate, coelomic …   Wiktionary

  • coelom — SYN: body cavity. * * * coe·lom sē ləm n, pl coeloms or coe·lo·ma·ta si lō mət ə the usu. epithelium lined body cavity of metazoans above the lower worms that forms a large space when well developed between the digestive tract and the body wall… …   Medical dictionary