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NOAA OKEANOS EXPLORER Program, Gulf of Mexico 2014 Expedition via Flickr Creative Commons // CC BY 2.0

Cephalopods Evolve Differently From the Rest of Us, Study Finds

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NOAA OKEANOS EXPLORER Program, Gulf of Mexico 2014 Expedition via Flickr Creative Commons // CC BY 2.0

The octopus is an animal with a seemingly endless amount of weird and wonderful traits, all the way down to its DNA. A new report published in the journal Cell has revealed yet another bizarre facet of cephalopod biology: the way they update their genes.

Coeloid cephalopods (that’s octopuses, squid, and cuttlefish) have evolved some truly mind-boggling abilities, from Houdini-like escape to crafting makeshift hunting blinds. They lack the standard optical equipment for color vision, yet scientists believe they can see in color anyway. And where warming waters have weakened other species, cephalopods populations appear to be booming.

The original cephalopod ancestor did not have all these traits. Their unique gifts, like ours, are the result of millions of years of evolution.

Animal evolution works like this: the genetic code of every member of a species is almost identical, but not quite. Each individual has a few DNA mutations that make it unique. When those mutations are advantageous in the environment, their owners will survive, reproduce, and pass the mutated DNA down to the next generation.

We also make changes to our RNA, but these are so scarce—in humans, just a few dozen sites amid roughly 20,000 genes—that their influence is relatively small.

But our rubbery-armed friends have apparently turned this system on its head. Researchers reviewing coeloid genomes say the cephalopods have evolved mostly through small, fluid changes to their RNA, and that their DNA doesn’t look like it’s been updated much at all.

The scientists found that around 11,000 of a squid’s 20,000 genes code for mutable RNA. Octopuses and cuttlefish genetics showed similar ratios, especially in the genes associated with their super-amazing, super-complex nervous systems. Nautiluses, those simpletons of the cephalopod family, looked more like us.

Liscovitch-Brauer et al. 2017. Cell.

Neurobiologist Clifton Ragdale of the University of Chicago was unaffiliated with the research but has worked on cephalopod genetics in the past. Speaking with Scientific American, he said the animals’ bizarro evolution scheme essentially represents “an alternative engine for cephalopod evolution.”

Ragsdale noted that scientists use DNA changes, not RNA, when determining evolutionary history. “This may mean that our molecular clock estimates of when different cephalopod lineages arose and diverged might be too recent. The Nobel Prize–winning biologist Sydney Brenner once said that octopi were the first intelligent beings on Earth. This could prove he was right.”

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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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