There are lots of strange things to discover in space, but flatworms sent to the International Space Station saved the really weird stuff for when they returned to Earth.
That's when one worm, which had been partially amputated before being launched into space aboard a SpaceX rocket in 2015, grew a second head.
Planarian flatworms are often used in biological studies because of their impressive ability to regenerate parts of their bodies after amputation. A set including both whole and amputated worms was sent to the ISS for a five-week stay and then evaluated back on Earth for an additional 20 months.
One of the space-flown worms regenerated into a rare double-headed specimen. That's something the researchers running the experiment from Tufts University say they'd never seen in their combined 18 years of maintaining a colony of more than 15,000 flatworms.
But that's just the beginning of the strangeness. When the researchers amputated both of the heads from the newly twin-headed worm, the headless middle section grew back two heads. In other words, something that happened after the worm was launched into space caused its body to be "reprogrammed" to consider itself to be some sort of new two-headed species.
The worms that left Earth whole also did odd things, including spontaneously splitting into two or more unique individuals. The scientists note, however, this could be a result of the different temperatures experienced by the worms during their space journey.
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