Deuterostomes (from the Greek: second the mouth) are one of the two superphyla of animals in the taxonomic branch bilateria, the other being the protostomes. These groups reflect two main lines of evolution based on their pattern of early development.
In both protostomes and deuterostomes, the embryo consists of a little hollow ball of cells known as a blastula. In deuterostomes early divisions of cells are parallel or perpendicular to the polar axis, and so the cells are located above and below one another; this is called radial cleavage. A groups of cells move inward to form an opening called the blastophore. In deuterostomes the blastophore develops to be the anus.
Deuterostomes have indeterminate cleavage: The cells' fate is not determined early on, and so 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.
Last but not least, Deuterostomes are enterocoely, which means the mesoderm forms as "out-pocketings" of the developed gut that will pinch off and form the coelom.
Deuterostomes (taxonomic term: Deuterostomia; from the Greek: "second mouth") are a superphylum of animals.
Deuterostomes are distinguished by their embryonic development; in deuterostomes, the first opening (the blastopore) becomes the anus, while in protostomes it becomes the mouth.
Deuterostomes display indeterminate cleavage - the cells' fates are not determined early on.
Compared to the protostomes, the deuterostomes are far less diverse, including among the invertebrates only the Echinoderms and a few minor taxa, but having as their main claim to fame the fact that Chordata belong to this sub-division.
The deuterostome condition is often associated with an initial embyonic cleavage pattern which is "radial" and in which cleavage planes are either parallel or perpendicular to the vertical axis of the embryo.
Deuterostomes also possess enterocoelous coelom development, in which the mesoderm arises as lateral outpocketings of the archenteron (embryonic gut) with hollows that become the coelomic cavities, and the development of the embryonicblastopore (the original opening) into the anus (rather than into the mouth as in most protostomes).
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