Deuterostomes
Deuterostomes
Deuterostomes (pronounced: doo-ter-uh-stohmz) are a major group of animals that includes vertebrates, echinoderms, and hemichordates. The term "deuterostome" is derived from the Greek words "deuteros" meaning "second" and "stoma" meaning "mouth". This refers to the developmental process in which the anus forms before the mouth in these animals.
Etymology
The term "deuterostome" comes from the Greek "deuteros" (second) and "stoma" (mouth). This is in reference to the embryonic development of these animals, where the anus forms before the mouth.
Characteristics
Deuterostomes are characterized by their embryonic development. In deuterostomes, the first opening (the blastopore) becomes the anus, while in protostomes, it becomes the mouth. Deuterostomes also have a dorsal, rather than a ventral, nerve cord and the formation of the skeleton and coelom are different in deuterostomes compared to protostomes.
Classification
Deuterostomes belong to the superphylum Deuterostomia. This superphylum is divided into three major phyla: Chordata, Echinodermata, and Hemichordata. The phylum Chordata includes animals such as mammals, birds, reptiles, amphibians, and fish. Echinodermata includes sea stars, sea urchins, and sea cucumbers. Hemichordata includes acorn worms and graptolites.
Related Terms
- Protostomes: The other major group of bilaterally symmetrical animals, in which the mouth develops before the anus during embryonic development.
- Blastopore: The first opening that forms in the embryo, which becomes the mouth in protostomes and the anus in deuterostomes.
- Coelom: The main body cavity in animals, which is lined with mesoderm and is located between the intestinal canal and the body wall.
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