McLean and Bagnall studied the motor neurons of baby zebrafish because the fish develop quickly and are see-through. They used state-of-art imaging techniques to monitor and manipulate neuronal activity in the fish.
"You can stare right into the nervous system," McLean said. "It's quite remarkable."
The separate circuits for moving the left and right and top and bottom of the fish allow the animal to twist its body upright when it senses that it has rolled too far to one side or the other.
"This arrangement is perfectly suited to provide rapid postural control during swimming," Bagnall said. "Importantly, this ancestral pattern of spinal cord organization may also represent an early functional template for the origins of limb control."
Separate control of dorsal and ventral muscles in the fish body is a possible predecessor to separate control of extensors and flexors in human limbs. By tweaking the connections between these circuits as they elaborated during evolution, it is easier to explain how more complicated patterns of motor coordination in the limbs and trunk could have arisen during dramatic evolutionary changes in the vertebrate body plan, the researchers said.
"We are teasing apart basic components of locomotor circuits," McLean said. "The molecular mechanisms responsible for building spinal circuits are conserved in all animals, so this study provides a nice hypothesis that scientists can test."
|Contact: Megan Fellman|