Dipleurula is a hypothetical

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

of the ancestral

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea ...

. It represents the type of basis of all larva forms of, at least, the eleutherozoans (all echinoderms except crinoids), where the

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ...

sea urchins Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

, sea cucumbers and

brittle stars Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

belong. The dipleurula is a bilaterally symmetrical,

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

ted echinoderm larva (cilia devoted to movement, feeding and perception). Dipleurula may represent an ancestral form for primitive

ambulacraria Ambulacraria , or Coelomopora , is a clade of invertebrate phyla that includes echinoderms and hemichordates; a member of this group is called an ambulacrarian. Phylogenetic analysis suggests the echinoderms and hemichordates separated around 533 ...

ns (and possibly even

deuterostomes Deuterostomia (; in Greek) are animals typically characterized by their anus forming before their mouth during embryonic development. The group's sister clade is Protostomia, animals whose digestive tract development is more varied. Some exampl ...

).Kardong, Kenneth V. 2006. Vertebrates: Comparative Anatomy, Function, Evolution, Fourth Edition, pp. 72–75. We can see that all well-known forms of larvae of echinoderms are derived from the hypothetical dipleurula. Among them fall the bipinnaria and the

brachiolaria A brachiolaria is the second stage of larval development in many starfishes. It follows the bipinnaria. Brachiolaria have bilateral symmetry, unlike the adult starfish, which have a pentaradial symmetry. Starfish of the order Paxillosida (''Astrope ...

of the

, the

auricularia ''Auricularia'' is a genus of fungi in the family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maint ...

of the sea cucumbers and the

pluteus larva An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea li ...

e of the

, and the sand stars. Also the doliolaria of the crinoids (sea-lilies and feather stars) can be attributed to the same basic pattern, even if they do not have a mouth opening.

References

External links

Information on forn
* Larvae Echinoderm biology {{developmental-biology-stub