Pyura chilensis: The "Living Rock"

Erin McCarthy

Sergio Majiluf via 

Pet rocks went out of vogue in the '80s, but an organism found off the coast of Chile and Peru might make you rethink the trend: These sea creatures masquerading as rocks are totally alive.

Crack open a Pyura chilensis and the sea creature—an immobile, invertebrate filter feeder that gets filed under the Ascidiacea class of "sea squirts"—practically bleeds vanadium, an elusive mineral found in crude oil. P. chilensis is commonly found in clusters of thousands, but reproduces solo: The organism is born male, but becomes hermaphroditic at puberty.

Two Chilean biologists, Patricio H. Manriquez and Juan Carlos Castilla, published their findings on the organism's asexual habits in 2005. To repopulate, P. chilensis releases clouds of eggs and sperm and waits for the two to collide.

Locals fish commercially for P. chilensis, and the rocky sea creature is something of a delicacy in Peru and Chile. It gets cooked into stews, prepared with salad and rice, or eaten raw. But non-locals aren't so wild about eating living rocks with living guts: the taste has been called everything from "soapy" to having "a weird iodine flavor." Bon appetit!