This Week in Zoology: Out of Sci-Fi and Into a Journal

I’m sure you’ve come across the phrase “stranger than fiction” before. This week, I came across a paper that I think fits this description perfectly. If you had seen this in a movie you would probably roll your eyes at it, unless it was the most wild of sci-fi.

And yet, it seems as though it happened.

Scientists decided to send some planarian worms to space. After 5 weeks at the international space station they returned to Earth.

And one of them came back with two heads. They tried chopping them off, but they just grew back. That worm has decided to remain a two-headed for the rest of its life now. So… that happened.

OK, we’re going to need a little more context here I think. Why did they do this in the first place? What is a planarian worm, and what is the relevance of all of this?


Planarian worms, besides being quite a cute representative of the flatworm phylum, are widely studied due to their amazing capacity for regeneration. Many animals have the ability to regenerate certain parts of their bodies, like the tail of a lizard, the leg of a newt or the retina of a zebrafish. Planaria, however, are partiularly awesome at it. Chop them up into pieces, and those pieces will just grow into a new worm. In fact, they will do this quite often of their own free will, splitting in half and allowing their tail end to grow into a new worm, at least when they decide to reproduce asexually. Scientists are therefore studying the underlying molecular mechanisms involved in regeneration, hoping perhaps to be able to apply this knowledge to the medical field. Could we, perhaps, find a way to “trick” our retinas into regenerating themselves after an injury, saving us a lot of time and pain? The whole field is fascinating.

Anyway, planarian worms are clearly exciting animals to work with. In this study, researchers wanted to know if the regenerative capacity of planaria was influenced by things like gravity, geomagnetic fields, etc. So, they chopped off their heads and tails, sent their torsos to space, left them there for a while, then brought them back to see what would happen.

The researchers found that many things about these worms were different when they came back to Earth, even after 20 months of reacclimatization on the home planet. Their behavior was different, as was their microbial composition. And, of course, this study grabbed plenty of attention because one of the worms came back looking like this


Usually, cutting up a planarian worm into three bits results in three new worms. When they tried this, however, the two head bits did regenerate into two new worms, but the middle bit just became another two-headed worm, albeit with an extra kink in its middle.


There’s no way around it… these animals are amazing.

I will let the researchers have the final say on what they hoped to gain from this study:

These observations may have implications for human and animal space travelers, but could also elucidate how microgravity and hypomagnetic environments could be used to trigger desired morphological, neurological, physiological, and bacteriomic changes for various regenerative and bioengineering applications.

Future space missions are being planned. I can’t wait to see what they find.

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