From the outside, it looks like no more than a rock – but break this thing open, and you’re in for a horror movie-caliber surprise. Though entirely immobile, it’s a living sea creature full of blood and guts. Pyura chilensis is found off the coast of Chile and Peru, and locals eat its bitter, iodine-rich flesh raw or in stews. The flesh is cut into small pieces and strung up to dry.
In the sea, P. chilensis simply blends in with all of the marine rocks, sucking in water and filtering out microorganisms. It’s born male, but becomes hermaphroditic, and reproduces by excreting clouds of both sperm and eggs into the surrounding water. The offspring start out as tiny tadpole-like creatures that eventually settle into stationary existence on the sea floor.
Learn more about this bizarre creature, and the experiment that enabled scientists to crack the mystery of its reproductive habits, at Scientific American.