# Dipleurula

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**Dipleurula** is a hypothetical [larva](/source/Larva) of the ancestral [echinoderm](/source/Echinoderm). It represents the type of basis of all larval forms of, at least, the [eleutherozoans](/source/Eleutherozoa) (all echinoderms except crinoids), where the [starfish](/source/Starfish), [sea urchins](/source/Sea_urchins), [sea cucumbers](/source/Sea_cucumbers) and [brittle stars](/source/Brittle_stars) belong. The dipleurula is a bilaterally symmetrical, [ciliated](/source/Cilia) echinoderm larva (cilia devoted to movement, feeding and perception).

## Etymology

Derives from [Ancient Greek](/source/Ancient_Greek) *di*, meaning 'two' and the small form of *pleura* (*pleurula*), meaning 'little side', i.e. 'little, two-sided [larva]'.[1]

## History

Although the term dipleurula stems from Semon (1888),[2][3] it was first systematically introduced, described and drawn by Bather (1900) in his monography on the echinoderms.[4] The name dipleurula, two-sided, was given to stress the fact that the larva of the typically five-rayed, (approximately) [radially symmetric](/source/Radial_symmetry) [adults](/source/Adults) show a bilateral structure. It was this bilateral structure of the larvae that identified echinoderms as [bilaterian](/source/Bilaterian) animals.

The original doliolaria schema shows a [benthic](/source/Benthic), crawling, larva. However Bather could not have known yet that larval echinoderms are typically pelagic (free-floating plankton).

## Structure

The hypothetical dipleurula larva bears resemblance to stages of all extant echinoderms, such as the [bipinnaria](/source/Bipinnaria) and the [brachiolaria](/source/Brachiolaria) of the [starfish](/source/Starfish), the [auricularia](/source/Sea_cucumber#Development) of the [sea cucumbers](/source/Sea_cucumbers), the echino[pluteus larva](/source/Pluteus_larva) of the [sea urchins](/source/Sea_urchins), and the ophiopluteus of the [brittle stars](/source/Brittle_stars). Also the [doliolaria](/source/Doliolaria) of the [crinoids](/source/Crinoids) (sea-lilies and feather stars) can be attributed to the same basic pattern.[2][5][6] Note, that the extant echinoderms represent just a small window on the extraordinary diversity of early echinoderms as known from their rich fossil record.[7] Although there is current research on fossilized larval skeletons,[8] the doliolaria remains a hypothesis.

The doliolaria shows a three-partite body, each of which develop paired coelomic spaces which originate from the [enterocoel](/source/Enterocoely). This, and their close resemblance to the [tornaria](/source/Tornaria) larva of [hemichordates](/source/Hemichordates), identifies them as [deuterostomes](/source/Deuterostomes).[2] The anterior coeloms are known as axocoel, the medial ones as hydrocoel and the posterior ones as somatocoels. In extant echinoderm larva, the coeloms on the right side of the larva are typically much smaller than the ones on the left side, or even rudimentary. The right hydrocoel may fuse with the right axocoel.[5][6]

## References

1. ["Lexikon der Biologie"](https://www.spektrum.de/lexikon/biologie/dipleurula/18496). Spektrum.

1. Hyman, Libbie Henrietta (1955). *The invertebrates. Vol. IV. Echinodermata*. New York: McGraw-Hill. p. 763.

1. Gupta, Tapashi (24 Feb 2021). ["Dipleurula Concept & Echinoderm Theory of Origin of Chordates"](https://medium.com/@tapashigupta/dipleurula-concept-echinoderm-theory-of-origin-of-chordates-51c36233f70d). Retrieved 7 May 2023.

1. Bather, F.A. (1900). *A treatise on zoology, Part III. The Echinodermata*. London, UK: Adam & Charles Black. p. 344.

1. Westheide, Wilfried & Rieger, Reinhard M. (2007). *Spezielle Zoologie, Teil 1: Einzeller und Wirbellose Tiere*. 2 ed. Heidelberg: Spektrum Akademischer Verlag. p. 976. ISBN 9783827415752.

1. Kardong, Kenneth V. (2006). *Vertebrates: Comparative Anatomy, Function, Evolution*. 4 ed. pp. 72–75.

1. Raymond C. Moore; Curt Teichert; P. A. Selden (eds.) (1967–2011). *Treatise on invertebrate paleontology (Part S-U) Echinodermata 1-3*. Kansas: Geological Society of America, University of Kansas.

1. Reich, Mike; Kroh, Andreas; Stegemann, Tanja R (2023). ["Larvalskelette mesozoischer Stachelhäuter (Seeigel, Seegurken und Schlangensterne) -- ein Überblick"](https://www.researchgate.net/publication/370592370_Echinodermata_2023_7_Arbeitstreffen_deutschsprachiger_Echinodermenforschender_Bremerhaven_27-29_April_2023_Arbeiten_Kurzfassungen_Echinodermata_2023_7th_Meeting_of_German_speaking_Echinodermologists_B). *Echinodermata 2023*. **7. Arbeitstreffen deutschsprachiger Echinodermenforscher**: 37. Boos, Karin & Reich, Mike (eds.). ISBN 978-3-910807-00-6.

## External links

- [Information on forn](http://scaa.usask.ca/gallery/lacalli/tutorial/deuterostomes.php)
- ["Dipleurula"](http://www.spektrum.de/lexikon/biologie/dipleurula/18496) (in German). *[Lexikon der Biologie](https://de.wikipedia.org/wiki/Lexikon_der_Biologie)*. Spektrum Akademischer Verlag. Heidelberg. 1999. Retrieved 2019-12-30.

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Adapted from the Wikipedia article [Dipleurula](https://en.wikipedia.org/wiki/Dipleurula) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Dipleurula?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.