Scientists have successfully demonstrated that a tadpole can see through eyes on its tail.
The study was conducted by a group of Tufts University biologists. They used 134 tadpoles of the African clawed frog "Xenopus laevis," surgically removing their eyes and placing new ones onto their tails.
"We do a lot of work to understand regenerative biology, and that entails experiments that change the body," says researcher Michael Levin. "We have four-headed worms, six-legged frogs, and many other unusual creatures here as part of our work on bioelectricity and organ regeneration."
After placing the eyeballs, the researchers found that they grew to roughly equal size. About half of the eyes sprouted nerve cells, some of which tapped into the spinal cord.
Mutated and normal tadpoles were then exposed to blue light or red light, the latter of which gave them a shock. Normal tadpoles avoided the red light but blind tadpoles did not. One fifth of the mutated tadpoles avoided the shocks.
This has important implications for the study of sensors in the body.
"These findings suggest that the brain has remarkable plasticity and may actually take a survey of its body configuration to make use of different body arrangements," Levin says. "If it were not the case, then every time a mutation produced an improvement in body plan — a large significant change in anatomy — the animal would die and the beneficial mutation would be lost."
If accurate, this new information could be implemented in anything from robots to prosthetic organs.
"This has implications not only for regenerative medicine — replacing damaged sensory and motor organs — but also for augmentation technology," Levin says. "Perhaps you'd like some more eyes, maybe ones that see in infrared?"
The scientists would also like to know which areas of the brain process this sensory data, the number of additional eyes a frog's brain can support and how the brain knows that a new organ is an eye.
Findings from the study were published on Wednesday Feb. 27 in the Journal of Experimental Biology.
