What is Pyura chilensis?
Pyura chilensis, native to Chile and Peru, is one of those exotic animals you may have heard of on TV shows. At first glance, it looks a little like a rock. On closer inspection, it turns out to be alive, with an outer layer composed of tunicin. Tunicine is a type of exoskeleton, but it is not made of bone. Rather, tunicin is a polysaccharide chain, similar to cellulose or chitin. In other words, P. chilensis has a kind of shell. Some sources claim that this shell is in fact made of cellulose, and that there is no such substance as tunicine. However, it was long thought that cellulose only occurred in plants, so it may be difficult for some people to accept that an animal could have a cellulose shell.
Weirder on the Inside
So far, this creature does not sound too strange. Keep in mind, though, that P. chilensis has no limbs, no legs or claws, no eyes, no mouth - no face of any kind, in fact. It looks, for all intents and purposes, just like a rock. In addition, it can't move. And it gets even weirder on the inside. Inside the tunicin exoskeleton, P. chilensis has a layer of skin and muscle, as well as clear blood. This gives the inside of the animal a bright red, wet appearance, much like the inside of a pomegranate.
P. chilensis, known in Spanish as piure, is classified as a sea squirt because it eats by inhaling water, extracting edible bits, and then squirting the water back out again. Sea squirts are one type of 'filter feeders,' a group that includes not only small, otherwise immobile creatures like P. chilensis, but also large animals such as baleen whales and some types of shark. The small, immobile filter feeders are called sea squirts.
Brightly Colored, but Not Poisonous
Most people in the northern hemisphere, if they ran into P. chilensis on the beach, would not even think to wonder whether this strange creature is edible. It certainly does not look edible (or even alive) on the outside, and when it's opened up, its bright red interior might lead spectators to think that it could be poisonous. It is true that brightly colored animals are often poisonous; striking color can act as a warning sign to other animals (including humans) in search of food. In the case of P. chilensis, however, no danger is present. In fact, in Chile, locals eat this animal with relish.
In addition to P. chilensis, other sea squirts, members of the Pyura genus, are commonly fished and eaten in Chile. These sea animals are eaten cooked with onion or raw, right out of the shell. Dried Pyura is sold on long strands, and individuals make a hobby out of swimming in search of them.
Vanadium in the Bloodstream
Sea squirts, including P. chilensis, contain high concentrations of the element vanadium in their blood. Vanadium is a transition metal which plays little or no role in the biology of most land-dwelling animals. Two exceptions to this rule are chickens and rats, which have been found to require small doses of vanadium in order to grow and reproduce correctly. Some humans take vanadium as a dietary supplement, but there is some evidence suggesting that it may be toxic.
Don't Ignore P. chilensis
P. chilensis is not well-known outside its native region, and perhaps the reason is that it does so little. Young P. chilensis attaches itself to a rock and remains there for the duration of its life cycle, unable to move. This does not make for a very interesting story or a very exciting nature documentary. However, the importance of P. chilensis to Chilean cuisine and culture, as well as the interesting characteristics of sea squirts, make this exotic creature worth a second look.