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岡部碩道 via Wikimedia Commons // Public Domain

Scientists Find Genetic Root of Limb Regrowth

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岡部碩道 via Wikimedia Commons // Public Domain

If you’ve ever been jealous of a lizard’s ability to regrow its tail, take heart: Scientists are one step closer to understanding how it works and say that one day we might be able to do the same thing. (With arms and legs, that is. Not tails. Be realistic.) They published their findings in the journal PLOS One.

Few things are cooler (and more useful) than the ability to regenerate lost limbs. So it’s not too surprising that scientists are really, really interested in how it all works. Researchers at the MDI Biological Laboratory in Maine were especially curious about the inner workings of a process called blastema formation, in which new limb tissue begins to grow at the site of a wound. They decided to look at three species with appendage-regenerating superpowers: the zebrafish (Danio rerio), the bichir fish (Polypterus senegalus) and Ambystoma mexicanum, better known as the Mexican salamander or axolotl. Despite this common trait, these species are evolutionarily distant from one another, having diverged about 420 million years ago.

In order to study limb regrowth, the scientists had to start with limb loss. They brought groups of axolotls, bichirs, and zebrafish into the lab and surgically amputated at least one appendage on each animal—legs for the axolotls and fins for the fish. Then they let the animals rest, collecting tissue samples from the wound sites every few days. They ran the tissue samples through a series of genetic tests, examining several types of each animal’s RNA in search of regrowth-related code.

Not only did they find that code, but they found the same code in all three species—a surprising and exciting twist. "It was a fantastic feeling," co-author Benjamin L. King said in a press statement. "We didn't expect the patterns of genetic expression to be vastly different in the three species, but it was amazing to see that they were consistently the same."

Understanding blastema formation could help explain the complicated science of wound and other tissue healing, and may someday lead to treatments for people who have suffered injuries or burns.

Co-author Voot P. Yin also notes that the regrowth mechanism they found may exist in many other species as well—including humans.

"Limb regeneration in humans may sound like science fiction, but it's within the realm of possibility," Yin said. "The fact that we've identified a genetic signature for limb regeneration in three different species with three different types of appendages suggests that nature has created a common genetic instruction manual governing regeneration that may be shared by all forms of animal life, including humans."

So don’t give up on your lizard dreams just yet.

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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Listen to the Impossibly Adorable Sounds of a Baby Sloth
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RODRIGO ARANGUA/AFP/GettyImages

Sometimes baby sloths seem almost too adorable to be real. But the little muppet-faced treasures don't just look cute—turns out they sound cute, too. We know what you're thinking: How could you have gone your whole life without knowing what these precious creatures sound like? Well, fear not: Just in time for International Sloth Day (today), we have some footage of how the tiny mammals express themselves—and it's a lot of squeaking. (Or maybe that's you squealing?)

The sloths featured in the heart-obliterating video below come from the Sloth Sanctuary of Costa Rica. The institution rescues orphaned sloths, rehabilitates them, and gets them ready to be released back into the wild.

[h/t The Kid Should See This]

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