Living stone: outside - cobblestone, inside - meat (11 photos)

This animal is as degraded as possible.





At first glance, this is a very ordinary sea rock, covered with a nasty slippery layer of algae, sand and mud. You can understand the difference if you take it in your hands - with a diameter of about 15 centimeters, the piura weighs about 115 grams, which is twice as light as your smartphone. An ordinary stone will be 10 times heavier.



Mmm, looks delicious!

Piuras often form colonies that look like real underwater rocks. All kinds of sea anemones, mollusks and plants can settle on them, just like on ordinary rocks — they are no different from non-living rocks. There are even large reefs off the coast of Chile and Peru, formed exclusively by piuras and their neighbors. How can you tell them apart from simple stone reefs? Take a closer look: the entire surface of living rocks is covered with pink spots. This is the mouth of each individual stone.





Several dozen piuras in one cluster.

Chileans know exactly where piuras live, how to distinguish them from inedible stones, and periodically dive into the ocean to get the main ingredient of a traditional dish for dinner. If you cut a boulder in half, there will be something inside that resembles a piece of beef. This is what is eaten. The "stone" shell is thrown away, like a pistachio shell.



The process of picking out the piur from the shell. The fleshy part of the "living stone" is called the "udder".

What the Chileans eat is, in fact, the entire inner world of the animal. And not primitive, but complete, with all the organs. They even have a spine! More precisely, they had one. So, let's figure it out, otherwise nothing is clear!



Here's whose inner world is really interesting to people!

Let's start from the beginning: piuras belong to the class of ascidians and the subtype of tunicates. These are very, very ancient creatures. They appeared when fish had not yet come out onto land - about 400 million years ago. Scientists say that on the evolutionary tree, piuras are closer to humans and other vertebrates than to worms and mollusks. That is, at the dawn of life, we had a common ancestor with living stones. How did it happen that we are now reading this text from the screen on the way to work, and it is difficult to distinguish a piura even from a stone? The fact is that the ancestors of all modern vertebrates followed the path of increasing the complexity of the body: they grew a spine, muscles, brains. But the ancestors of the piura decided not to bother and trudged in the opposite direction of development! The inner world of a living stone was simplified to the maximum.



This is what the piura shell looks like from the inside. They live in the recesses!

Piura are filter feeders. They draw water through the mouth, after which it enters the pharynx. Here are the gills through which gas exchange occurs, and special cells that secrete mucus. This mucus envelops the smallest edible particles that the piura has sucked in with the liquid. After digesting the nutritious suspension, the waste product is thrown out through another hole. That's it, such a simple way to get something to eat. It will work even in the conditions of the apocalypse.



How can you resist and not bite off a piece?

Reproduction is also simple for them. Piura are hermaphrodites. To make babies, tunicates alternately throw out female and male reproductive cells into the water - and that's it! Usually piuras live in colonies, so they don't need to look for a partner, they are always nearby. But if suddenly not, then the animal will fertilize itself and create a new colony.



When you were a very bad child, and Santa Claus brought you this instead of a present.

It is also very interesting how living stones turned into, in fact, stones. Pay attention to their hard outer shell. No other creature living on Earth has such armor! It's all in the composition - it is made of a special type of cellulose called tunicin. In fact, any cellulose is the prerogative of plants, not animals. Shells and carapaces are made of calcium and collagen, while the hard covers of insects are made of chitin. Animals and insects cannot produce cellulose because it is a plant building material. How did the piur manage it then?



This is what you can turn into if you degrade forever!

You could say they stole this ability from bacteria. This is called horizontal gene transfer - when the DNA of one species of living creatures crosses with another species not directly, through the mating of species, but in the case of a genetic error. Apparently, a long time ago, the genes of bacteria that can synthesize cellulose got into the sex cells of piur. The DNA was integrated into the genes of the then not-yet-stones, and the first tunicates were born - creatures with armor made of tunicate. Evolutionarily, having a shell made of such a hard material turned out to be very advantageous, so the animals turned themselves into living stones.



Each piece, similar to a solid stone, consists of a couple of dozen piura.

At the same time, at the larval stage of development, piura do not look like stones at all - they look like small tadpoles. Piura have the beginnings of a spine, they can swim independently, distinguish light and shadow, and can maintain balance. But as soon as the fry finds a suitable place on some rock or a colony of its own kind, it will attach itself to the substrate and begin to degrade. Gradually, the spine and all the organs responsible for movement will dissolve, and it will turn into a living stone.



Pyura is not only scraped from the bottom of the sea, but also grown on special farms.

Despite such an unsightly appearance, pyura even has its own predators - mollusks, some fish and, of course, people. Not everyone dares to try the delicacy, because the pebbles have a specific taste. In the process of filtering, the animals accumulate a colossal amount of vanadium and other heavy metals. Those who have tried it say that eating pyura is like jumping into the sea with your mouth open. You immediately feel all the tastes of the sea - here you have mussels, scallops, and sea urchins. Delicious, but not for everyone.