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Left photo: A. Diamant. Right photo: P. Cartwright

Microscopic Parasite Revealed to Be Teeny, Tiny Jellyfish

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Left photo: A. Diamant. Right photo: P. Cartwright

Forget everything you thought you knew about myxozoans. (We know it’s hard, but you can do it.) Scientists sequenced the microscopic organisms’ genome and discovered that they’re actually a type of teeny tiny jellyfish. The researchers published their results in the Proceedings of the National Academy of Sciences

Compared to other animals, the body of the jellyfish is as simple as it gets. It’s pretty much a bag with a single hole that serves as both mouth and anus. The bag is ringed with tentacles, and each tentacle is tipped with nematocysts, or stinging cells.

But compared to the myxozoans, most jellyfish are practically sophisticated. Myxozoa is the name of a group of more than 2000 different species of minuscule parasitic organisms that infect fish and other sea creatures. The myxozoans are incredibly primitive, made of just a few cells each. They don’t even have mouths. They do, however, have nematocysts—a defining characteristic of a jellyfish.

The little critters are “really weird,” ecologist Paulyn Cartwright said last week in a press release. When Cartwright and her colleagues at the University of Kansas sequenced the myxozoan genome, they found two surprises. The first was that the parasites are actually “micro jellyfish.”

"Because they're so weird,” Cartwright continued, “it's difficult to imagine they were jellyfish." And were may be the operative word: Cartwright and her colleagues believe that the myxozoans may have once been full-bodied cnidarians (the phylum that includes jellyfish), as opposed to the "highly reduced" ones they are now. But their body plans degenerated until there was nothing left but a few cells. Their bodies are so simple that for many years, scientists believed they were single-celled organisms.

"This is a remarkable case of extreme degeneration of an animal body plan," Cartwright said. "First, we confirmed they're cnidarians. Now we need to investigate how they got to be that way."

The second surprise lay in the genome itself. The typical cnidarian genome has 300 million base pairs. The myxozoan genome has only 20 million. "These were 20 to 40 times smaller than average jellyfish genomes," Cartwright said. "It's one of the smallest animal genomes ever reported.”

The reclassification of the myxozoans into the cnidarian group challenges basic scientific ideas about the animal kingdom.

Certain genes, like the Hox gene, are considered crucial to animal existence. But the myxozoans don’t have Hox genes. They don’t have much of anything. They’re definitely cnidarians; their genomes, however dinky, confirm it. 

“But animals are usually defined as macroscopic multicellular organisms,” Cartwright said, “and this is not that. Myxozoa absolutely redefines what we think of as animal."

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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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