A 520-million-year-old fossil shows how the nervous system of early animals evolved, shedding light on the development of our earliest ancestors. This spectacularly well-preserved relic is the most-detailed example of a preserved nervous system, researchers report, showing detail fine enough to discern individual nerve fibers.
Chengjiangocaris kunmingensis was a member of a group of arthropod ancestors known as fuxianhuiids. Studying these well-preserved nerves could allow researchers to uncover how arthropods, animals with jointed legs, developed long ago. This group of animals includes spiders, crustaceans, and insects.
Most animal groups present around the world today first came into being during the Cambrian Explosion, a time period half a billion years ago, when life experienced a great increase in diversity.
The fossil of the ancient crustacean-like animal was discovered in southern China.
"This is a unique glimpse into what the ancestral nervous system looked like. It's the most complete example of a central nervous system from the Cambrian period," Javier Ortega-Hernández, a zoologist from the University of Cambridge said.
The central nervous system of animals coordinates activities of the body, including both automatic and voluntary movements. However, the structures of these systems can be radically different between various species. In humans and other vertebrates, the nervous system is composed of a brain and spinal cord. However, arthropods utilize a small brain and ganglia - pearl-like structures of nerve tissues.
The fossil shows C. kunmingensis possessed a hybrid system, featuring a nerve cord, similar to a spinal cord, in addition to a network of ganglia. Each pair of legs in the animal were driven by a single on of these structures, resembling a pearl necklace.
The nerve cord of the creatures possessed a series of nerves emanating from the central structure, similar to the anatomy of modern velvet and penis worms. This layout has been lost in contemporary arthropods, as well as water bears.
Future research will examine other fossils from the Cambrian Explosion, in an effort to better understand how nervous systems evolved in animals more than 500 million years before our own time.
Research into the uniquely-preserved fossil and what it can tell us about the evolution of animals, including humans, was profiled in the Proceedings of the National Academy of Sciences.
