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G. P. Schmahl, NOAA FGBNMS Manager via Wikimedia Commons // Public Domain

The Christmas Tree Worm Has Eyes on Its Gills

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G. P. Schmahl, NOAA FGBNMS Manager via Wikimedia Commons // Public Domain

The Christmas tree worm, Spirobranchus giganteus, has some flashy gills. While the worms bury themselves in coral, only their colorful fir-shaped radioles—appendages they use for respiration and eating—are visible. They also make the world visible to the worm: That's where their eyes are located.

Their bright-orange eyes are hidden inside the creature's gills. If you look very closely, you can see them tucked away in the darkest-colored part of the animal like Christmas presents with neon wrapping paper.

Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0

 
The Christmas tree worm’s obscured peepers might be the only example of eyes located on gills in the animal world, as marine biologist Michael Bok told ScienceNews. Unfortunately for the worm, eyes shrouded by branch-like gills can be limiting. The Christmas tree worm can only see what’s directly in front or behind it, and when a shadowy predator passes by, the worm sucks its radioles down out of sight. Bok calls the worm’s eye position “really silly.” But, since most other fan worms don’t even have eyes at all, the Christmas tree worm is actually pretty far ahead in the visual acuity game.

Scuba divers from the Indo-Pacific to the Caribbean are fond of spotting the creatures on coral reefs, but they have to maintain a little distance lest they spook the worms into hiding. Earlier this year, scientists from UCLA studying this hiding behavior among Christmas tree worms in Mo’orea, French Polynesia, found [PDF] that the animals don't seem to find strength in numbers: The more worms in an area, the more time individual worms spent hidden in the coral. Conversely, worms with only a neighbor or two spent more time in the open. It's possible that a lot of eye-catching radioles in one place make the worms far too conspicuous to their predators, which include sea urchins, sea stars, flounders, and stingrays.

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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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