Sea urchins share our genes, research reveals

HUMANS and sea urchins are unlikely cousins, a blueprint of the sea-creature’s genetic code has revealed.

The spiky invertebrates are more closely related to people than either flies or worms, and share more than 7,000 of the same genes, scientists have found.

Within urchin DNA are genes associated with many human disorders, including muscular dystrophy and Huntingdon’s disease.

Other genes are involved with taste, smell, hearing, balance and — surprisingly — vision.

Sea urchins can apparently see, or at least sense, light through their feet.

Another unexpected find was the fact sea urchins have a unique and complex immune system which in some respects outperforms that of much more advanced animals.

An international team of experts described the sea urchin genome today in the journal Science. They identified a total of 23,300 genes made from 814 million letters of DNA code taken from the Californian purple urchin, strongylocentrotus purpuratus.

The sea urchin was already widely used by scientists analysing the genetic networks that control biological development.

With its ability to lay millions of eggs in a lifetime and transparent embryos that reveal all their working parts, the creature is ideal for observing what happens after conception.

One of the biggest surprises was the discovery that the animals have a sense of vision.

Professor Gary Wessel, a member of the Sea Urchin Genome Sequencing Consortium from Brown University in Providence, Rhode Island, US, said: “I’ve been looking at these organisms for 31 years — and now I know they were looking back at me.”

The urchin’s vision genes are activated in its tube feet, tiny projections on the creature’s shell that help it move and feed.

An extraordinary number of genes encode for molecules that play a part in the sea urchin’s natural immune system, the scientists found. This part of the body’s defences involves an array of pre-formed receptors on cells that respond to different kinds of foreign invader.

Sea urchins have roughly ten times more of these receptors than vertebrates, the genome revealed.