4 mars 2016

Le plus ancien système nerveux


Extrait de la fascinante nouvelle:

Fossils of an ancient creature resembling a shrimp with an armored head contain the oldest and best-preserved nervous system ever found, which could help scientists decipher the evolution of nervous systems in animals alive today, according to a new study.

The remarkable remains belonged to Chengjiangocaris kunmingensis, a crustaceanlike creature that lived 520 million years ago in what is now South China. The fossils revealed a long "ropelike" central nerve cord that extended throughout the body, with visible clusters of nerve tissue arranged along the cord, like beads strung on a thread. Even individual nerve structures could be detected, the scientists discovered.

They noted that the nerve tissue masses, or ganglia, grew progressively smaller along the central nerve cord, with the smallest masses being the ones most distant from C. kunmingensis's head. The researchers also found that the ganglia were associated with pairs of legs, which also reduced in size as they progressed along the animal's body.



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