Psyche, Science, and Society

Vertebrates and earthworm nervous systems share common origin

April 22nd, 2007

A new study examining the microstructure of the central nervous system (CNS) of earthworms suggests that they share the same evolutionary origin as do th CNS of vertebrates, in contrast to received wisdom:

Vertebrates have a spinal cord running along their backs, but insects and annelid worms such as earthworms, which have simple organs that barely resemble a brain, have clusters of nerves organized in a chain along their bellies. So biologists have long assumed these systems—key to ultimately putting a brain to use—arose independently, only after the split.

In the new study, researchers at the European Molecular Biology Laboratory [EMBL] in Heidelberg examined they embryos of a marine annelid worm called Platynereis dumerilii, which has a nervous system unchanged for eons. They documented the molecular fingerprints of the developing nerve cells.

“Our findings were overwhelming,” says study team member Alexandru Denes. “The molecular anatomy of the developing CNS [central nervous system ] turned out to be virtually the same in vertebrates and Platynereis. Corresponding regions give rise to neuron types with similar molecular fingerprints and these neurons also go on to form the same neural structures in annelid worm and vertebrates.”

“Such a complex arrangement could not have been invented twice throughout evolution , it must be the same system,” said Gáspár Jékely, another team member. “It looks like Platynereis and vertebrates have inherited the organization of their CNS from their remote common ancestors.”

Entry Filed under: Neuroscience, Psychology, Science