How newts transformed our understanding of space travel

SOURCE: Grigoryan, E. N., Mitashov, V. I., & Anton, H. J. (2002). Urodelean amphibians in studies on microgravity: effects upon organ and tissue regeneration. Advances in Space Research, 30(4), 757-764. https://doi.org/10.1016/S0273-1177(02)00392-7

Pleurodeles waltl

If your favorite animal is anything other than the Iberian ribbed newt, Pleurodeles waltl, I firmly believe you should reconsider. Here’s why:

  1. Pleurodeles waltl have the most epic defense mechanism of all time. When attacked, they can rotate their ribs until the sharp, bony ends pierce through their skin and create protective spikes to ward off predators.
  2. But that’s not all. At the same time, the newts secrete a sticky, milky, poisonous goo that coats their skin. When the ribs pierce through the skin, they get coated in this goo, turning the ribs into weapons that stick poison directly into a predators bloodstream.
  3. Newts and other salamanders have a really interesting (if not particularly flattering) cultural history. For example, during the middle ages, witches were said to summon demons using a form of brandy made from salamanders.
  4. Pleurodeles waltl can regenerate their limbs, spinal cord, heart tissue, brain cells, and even their eyes.
  5. Pleurodeles waltl have been on at least six different space missions. 

In this article, I’m going to focus on the story behind number five: how did Pleurodeles waltl become the world’s favorite amphibious astronauts?

Four images in a 2x2 square. The top photos show x-rays of newts. On the right, the newt's ribs have rotated outwards to poke through the skin. The bottom images are simplified diagrams of the same images, including annotations for the angle of the ribs
Pleurodeles waltl can rotate all of their ribs until they pierce through the skin to avoid being eaten. This image shows Pleurodeles waltl in a resting position on the left and after mild aggression on the right. Heiss et al., 2010, open access.

The story starts in the late 1990s with a team of three scientists from Russia and Germany (although this is not the first time newts had been to space!). Their goal? To better understand how space affects the process of regenerating tissue in humans and other animals. With the ability to regenerate virtually every part of their body, Pleurodeles waltl was the perfect model organism. 

Newts on a plane
Man holding a small container with a newt in it
STS-65 Mission Specialist Donald A. Thomas observing a newt on a space shuttle in 1994. Credit: Wikimedia Commons.

In this particular experiment, the researchers wanted to look at how space travel affects regeneration of a part of the body called the neural retina. The neural retina is the web of nerve cells inside your eye (and the newt’s eye) that send signals from light-sensing cells in the eye (rods and cones) to your brain. To test this, they divided 30 newts into two groups: one received an eye surgery to damage the retina four weeks before the experiment started, while the other received the surgery two weeks before the experiment. At the start of the experiment, those 30 newts were evenly divided into three more categories: one group stayed on land over the course of the experiment, one spent two weeks in space, and the final group was sampled immediately to get a “before” picture of how the newts’ retinas looked before the experiment. 

Once the experiment was cleared for takeoff, the researchers sent 10 newts off on their big adventure.

For two weeks, these newts traveled through space, orbiting the earth on the Bion-11 biosatellite. Meanwhile, 10 newts in identical cages sat in the lab back on earth.

After two weeks, the researchers gave each newt an injection containing some building blocks of DNA so that they could trace to see how fast each newt was building new cells. The next day, they preserved all of the newts and examined them to visually classify how much of each retina had regenerated. 

What did they find?

Interestingly, for the newts that had the eye surgery two weeks before the experiment, the retina regenerated way faster if they went to space. The researchers saw this both in the physical appearance of the retina and the rate at which it was building new cells. 

For the newts that had the surgery earlier (four weeks before the experiment), most were already pretty well healed by the start of the experiment and there wasn’t quite as much of a difference between the flight crew and their earth-bound parallels. 

This may seem surprising, but it is exactly what the researchers expected. As it turns out, most of their previous experiments confirmed the exact same phenomenon: newts are able to regenerate their lens, legs, and tail faster if they take a quick trip into outer space right after they get hurt.

But why?
Two newts swimming in a large tank
Iberian ribbed newts (Pleurodeles waltl). Credit: wikipedia

Honestly, while it is really clear that this is happening, it is much less clear why. There is some evidence that calcium levels change in the newt’s body under conditions of really low gravity, and that may lead to changes in the levels of an important hormone for tissue regeneration, but these results have yet to be confirmed.

There is some belief that the potentially terrifying experience of being packed up in a spaceship and sent out of the atmosphere may cause higher levels of stress that could affect the process of regeneration. However, previous tests have shown that using a machine to decrease gravity for newts on earth still causes them to regenerate faster, while stressing them out in other ways does not. It is possible that there is a specific stress protein associated with low gravity, but such a protein hasn’t been identified to date.

At the time this study was written, there were still lots of unanswered questions about why this happens. But we know for sure that space travel speeds up the rate that newts can regenerate most parts of their body. 

Could humans heal faster in low-gravity as well? Is there any long-term cost to healing so quickly? Why does this happen? To learn more, we’ll probably have to do a few more studies on your new favorite animal, the space-traveling newt, Pleurodeles waltl.

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Abigail Lewis

I am a fourth-year undergraduate at Pomona College with interests in limnology, microbial ecology, and nutrient cycling. In between rehearsals, hikes, and long dinners I am working to build a career that will address environmental issues and build a more inclusive scientific community.

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