Deuterostome

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• Echinodermata
• Hemichordata
• Chordata
• Chaetognatha

Deuterostomes (taxonomic term: Deuterostomia; from the Greek: "other mouth") are a superphylum of animals. They are a subtaxon of the subregnum Bilateria, and are opposed to the protostomes. Deuterostomes are distinguished by their embryonic development; in deuterostomes, the first opening (the blastopore) becomes the anus, while in protostomes it becomes the mouth.

Related Topics:
Animal - Taxon - Bilateria - Protostome - Embryonic development - Blastopore - Anus - Mouth

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There are three phyla of deuterostomes:

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• Phylum Chordata (vertebrates and their kin)
• Phylum Echinodermata (starfishes, sea urchins, sea cucumbers, etc.)
• Phylum Hemichordata (acorn worms)

The phylum Chaetognatha (arrow worms) and the isolated genus Xenoturbella may also belong here. Extinct groups may include the phylum Vetulicolia.

Related Topics:
Chaetognatha - Xenoturbella - Vetulicolia

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In both deuterostomes and protostomes, a zygote first develops into a hollow ball of cells, called a blastula. In deuterostomes, the early divisions occur parallel or perpendicular to the polar axis. This is called radial cleavage, and also occurs in certain protostomes, such as the lophophorates. Cleavage is indeterminate - the cells' fates are not determined early on. Thus if the first four cells are separated, each cell is capable of forming a complete small larva, and if a cell is removed from the blastula the other cells will compensate.

Related Topics:
Blastula - Radial cleavage - Lophophorate

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In deuterostomes the mesoderm forms as evaginations of the developed gut that pinch off, forming the coelom. This is called enterocoely.

Related Topics:
Mesoderm - Coelom - Enterocoely

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