These Rocks Are Bleeding, Because OMG WTF

by Laurel Walsh


You can’t unsee it. Usually if you crack a rock open, you just find more rock. But apparently some rock innards are a bit more barfy.

The “Pyura chilensis” is a mysterious sea creature delightfully known as “period rock” to those who handle it. It’s found on the coasts of Chile and Peru, and it’s pretty boring on the surface: it looks like a rock, feels like a rock, and acts like a rock. It sits on top of other rocks and never, ever moves. So why is there blood in it?! Gahh!

According to the Scientific American, Pyura chilenses wear thick “tunics” made of hard molecule compounds called tunicin. These tunicin shells give Pyur chileneses their rock-like appearance, and help them do what they do best – sit still and do nothing.

The inside of the tunics are lined with the Pyura chelenses’ skin, muscular bands, and bloody chamber parts that inhale and exhale water. Period rocks eat by absorbing tiny, nutrient-rich algae fibers floating around the sea.


Probably looks something like this.


Pyura chelenses are fished commercially and eaten by the locals, raw or cooked, paired with rice or salad. Fishermen hack open the sea creatures and take the meaty stuff out. My vegan brain has negative five million percent interest in putting that in my mouth, but to each her own.

Here she is all cooked up:


So close and yet so far from being tomatoes.


Period rocks also aren’t the only surprise-it’s-alive creatures floating around the seaside: Scientific American says they belong to a whole class of “sac-like marine invertebrate” otherwise known as “sea squirts.” Rocks have (almost) never been so sexual. Try not to think about this the next time you swim in an ocean, skip a stone, or walk on any ground anywhere ever.


Thanks to Death and Taxes.

Images via Scientific American, College Candy, and Death and Taxes.

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