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Assignment: Impossible

Assignment: Impossible


Exploring the area between the unknown and the impossible.
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A Menagerie of Curiosities: Eyes on their tails

The views expressed are those of the author and are not necessarily those of Scientific American.


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In A Menagerie of Curiosities, I explore the fascinating results of experiments that explore how life develops.

A tadpole missing eyes on its head that had an eye implanted on its tail. Credit: Douglas Blackiston.

Science to me is about exploring what’s unknown and what’s impossible. So what happens if you implant eyes onto a tail of a blinded tadpole? One might not expect anything — the brain of a tadpole didn’t evolve to find an eye on its tail. But developmental biologist Michael Levin at Tufts University and his colleagues discovered these eyes can help tadpoles see again, helping reveal how adaptable the brain is. (For more images, look at this photo gallery.)

Crazily enough, the eyes survive the destruction of the tail during tadpole to frog metamorphosis and end up healthy. On the frogs’ butts.

A frog with an eye on its behind. Credit: Douglas Blackiston.

I’m actually familiar with bizarre tadpoles — I wrote my baccalaureate thesis on headless tadpoles and the brou-ha-ha that erupted over wild claims such research would lead to human organ factories based on headless clones. Never mind artificial wombs currently don’t exist, so one would have to find women to raise such clones inside them. Never mind headless clones wouldn’t survive to term.

Top: Headless tadpole. Middle: Regular tadpole. Bottom: Tailless tadpole.

When I asked Levin if he felt weird painstakingly grafting eyes into the tails of tadpoles, he said such research was actually normal for him — “we have four-headed worms, six-legged frogs, and many other unusual creatures here as part of our work on bioelectricity and organ regeneration.”

Four-headed worms? Six-legged frogs? Frogs with eyes on their butts? I’m launching a new feature here to highlight these strange, extraordinary creatures.

The name for what I hope will be a weekly series, “A Menagerie of Curiosities,” refers to the wonder rooms and cabinets of curiosities that housed anomalies and mysteries in Renaissance Europe and ultimately served as the forerunners of museums. (A great modern cabinet of curiosity is the Museum of Jurassic Technology in Los Angeles, featured in the book “Mr. Wilson’s Cabinet Of Wonder,” both of which I highly recommend.)

A display of such oddities might undoubtedly come across as a circus freak show, and I won’t deny a certain morbid curiosity on my part with such work. But these experiments aren’t done for sport — they shine a light on how the fundamentals of life work. For instance, these findings are evidence the brain may survey its body to figure out what it can do instead of limiting use of its body parts to expected roles. If this were not the case, every time a mutation led to an anatomical improvement, the change would be useless and the animal might die and not pass on its beneficial mutation. As such, the brain’s adaptability makes it easier for complex new body features to evolve.

Ultimately, Levin hopes this work can help treat blindness and other sensory disorders, by testing how adaptable the nervous system is to, say, implants that could help people see. Furthermore, such research could not only help replace lost senses, but augment people with new ones — anyone want infrared vision?

Charles Q. Choi About the Author: Charles Q. Choi is a frequent contributor to Scientific American. His work has also appeared in The New York Times, Science, Nature, Wired, and LiveScience, among others. In his spare time, he has traveled to all seven continents. Follow on Twitter @cqchoi.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Ingamas 6:04 pm 03/4/2013

    In hindsight that might be a good place to have an (Working )eye if you are a frog.

    Under sensory disorders : Can we work on common sense?

    Link to this
  2. 2. jtdwyer 6:10 pm 03/4/2013

    Who’s responsible for all the people whose heads are up their butts? Sorry <%)

    Link to this
  3. 3. jonathanseer 7:19 pm 03/4/2013

    So close yet so far = failure in the eyes of the researcher who put the eye on the behind of a frog.

    He or she was aiming for the anus very specifically in hopes of giving the brown eye true sight LOL

    Link to this
  4. 4. jonathanseer 7:20 pm 03/4/2013

    Also left unsaid is their motivation was simply having fun. When they realized they had to justify what they were doing they came up with the genetic research angle (joke)

    Link to this

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