Sea urchins are echinoderms (Greek for spiny skin), marine animals that originated over 540 million years ago and include starfish, brittle stars, sea lilies, and sea cucumbers. Following the great extinction of animals 250 million years ago, the modern sea urchins emerged as dominant echinoderm species. The purple sea urchin emerged in the North Pacific Ocean during a rapid burst of speciation and diversification 15-20 million years ago.

There was great interest in the sea urchin as a target for genome sequencing because these animals share a common ancestor with humans, scientists said. That ancestor lived over 540 million years ago and gave rise to the Deuterostomes, the super phylum of animals that includes phyla such as echinoderms and chordates, the phylum to which humans and other vertebrates belong.

All Deuterostomes are more closely related to each other than they are to any other animals not included in the Deuterostome super phylum. For example, among sequenced genomes, the genomes of fruit flies and worms are more distant from the sea urchin genome than is the human genome.

"This analysis shows that sea urchins share substantially more genes and biological pathways with humans than previously suspected," said Francis Collins, director of the National Human Genome Research Institute at the National Institutes of Health, which supported the research. "Comparing the genome of the sea urchin with that of the human and other model organisms will provide scientists with novel insights into the structure and function of our own genome."

To discover how sea urchins and humans can be so different, yet be related by descent from an ancient relative, their genomes were compared. The sea urchin is an invertebrate and the first example of a Deuterostome genome outside
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Contact: Cheryl Dybas
cdybas@nsf.gov
703-292-7734
National Science Foundation
9-Nov-2006