Franken-Tadpoles Can See Out of Eyes in their Tails
It sounds like the work of a mad scientist in a comic book: researchers from Tufts University implanted eyes on the tails of tadpoles. They wondered whether the eyes would simply sit there, uselessly, or would tadpoles be able to see out of them? According to the recent study, the tadpoles can indeed see out of these eyes attached to their tales, even though they are not directly attached to their brains. The results of the study may have profound implications for future work in robotics and in prosthetics.
According to the Boston Globe, the researchers started by transplanting the eye of one tadpole embryo onto the backside of the other. They did this 230 times. Nearly every time, the tadpoles' third eyes were about the same size and shape as the ones on their heads and faced outward. In a significant portion of these tadpoles, the eye connected to the spine through nerves. Then the researchers removed the eyes of the heads of the tadpoles.
Then the researchers performed an experiment with two lights, a red and blue. All of the tadpoles were exposed to blue and red light but, with exposure to the red light, the tadpoles would receive a shock. Tadpoles who could see out of their normal eyes learned to avoid the red light. Tadpoles who were blind did not learn to avoid the red light, presumably because they could not see it.
However, among the tadpoles who had been blinded but had an eye on their tale that connected to their spine, one in five were able to learn to avoid the red light as well. Presumably, that means that the animal could see.
The study could be exciting for manufacturers who want to build, say, more than a glass eye. It also is exciting for robot manufacturers, who could build robots who, if they have a new arm implanted, would not require the use of entirely new software.
In addition, for those who are curious, the scientists wondered whether the eyes on the tadpoles' tales would fall off or keep working when they became frogs. In fact, the frogs do have eyes on their butts.
The study was published in the Journal of Experimental Biology.