What if I told you that there existed a rock-like sea creature that lives on the coast of Chile and Peru that, when you cut it open, has bloody guts resembling a tomato? And what if you could eat that rock?

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Lurking off the coast of Chile and Peru lives a sea creature that blends in so naturally with the rocks on which it lives you’d be forgiven for missing it.

However, if you were to accidentally stand on this living rock it will burst to expose a mass of blood-red hermaphrodite creatures considered a delicacy in the nearby Central American countries.

Thankfully, according to Scientific American, all of this is possible. The creature, called Pyura chilensis (or, as some people brashly refer to it, a Period Rock), is an immobile, sac-like invertebrate. To eat, it filters out microalgae from inhaled ocean water. To spawn, the hermaphrodite rocks spew eggs and sperm into the surrounding ocean in a fertile cloud. With any luck, following any sperm-egg collisions, more rocks will be born, or at the very least, a tourist’s late-night skinny-dipping session will be ruined by disgusting reproductive rock juice.

The best part is that the creatures are edible, and are typically eaten by locals with salad and rice.

Pyura chilensis is known as a tunicate, endemic to the shallow waters of Chile and Peru. This marine invertebrate animal is a filter feeder that absorbs microorganisms out of sea. It is a member of the phylum Tunicata and serves as an immobile animal enveloped in a hard collection of outer cells that allows it to attach to surfaces.

Its exterior perfectly resembles the visual texture and color of a rock, but its interior is comprised of tissue, blood, and living structures just like any other animal of its class. Pyura chilensis utilizes two tunicin structures for feeding, by inhaling water and filtering out excrement liquid through the other end.

The most interesting feature of this bizarre creature, however, is its reproductive skills.

The Piure is born a male and when it reaches puberty it also grows female organs, making the sea squirt a hermaphrodite.

When it comes to breeding season, the Piure releases eggs from its female organs at the same time it releases sperm from its male gonads into the seawater.

If the eggs and sperm collide they form a ‘fertile cloud’ that will produce tadpole-style children.

These male tadpoles will then settle onto a nearby rock and grow into adults.

Piure’s only breed like this when they are alone; if there are other members of the species nearby, the creature will choose to cross-breed to increase the chances of success.

Despite its red color, the blood of the Piure is clear.

It also contains a high level of vanadium – a hard, silvery grey metal that occurs naturally in more than 60 different minerals around the world.

According to Scientific American magazine, the concentration of vanadium produced by the Piure is around ten million times the amount found in the surrounding seawater, and researchers are unsure what the function this element has in these creatures.

On land, vanadium is used to make steel alloys.

The animal is one of the main food sources for aquatic species such as the Chilean abalone but it also fished commercially and served in Chilean restaurants.

The living rock has to be cut using a sharp knife or handsaw before the siphons are pulled from the tunic.

This flesh is canned or sold as strips and can be eaten raw, or cooked. It is also exported to Sweden and Japan.

Because of its high level of vanadium, and the element’s toxicity, there are concerns about eating the creature.

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