THE OCTOPUS GENOME.

Disturbing and intelligent, unsightly but skilled in the arts of camouflage, unusual and has two eyes in his lineage and too similar to ours to ignore, the octopus is probably the closest thing to an alien we know on Earth. Reading the complete DNA Octopus  now explains the presence of all these advanced qualities in an invertebrate that, for all we know, it should not have them.

The octopus has the highest nervous system of invertebrates, along with camera-type eyes like ours, prehensile arms and complex behavior. The genome reveals that his repertoire of genes in the nervous system is typical of invertebrates, but has expanded greatly two families of genes, as it was thought that only happened in vertebrates. These serial gene duplications of development are an essential topic of evolution as a whole.

An international team coordinated by the universities of Chicago and California at Berkeley has sequenced the genome   Octopus bimaculoides,   California's two-spotted octopus, which becomes the reference genome of cephalopods, the strange family of octopus, cuttlefish and squid. Although an animal genome is rarely news in our genomes saturated days, this is enough information to have deserved   Publishing   Nature . In addition, the consortium not only describes their genes, but their expression in 12 different tissues of the animal.

Genetic harvest has been good, with hundreds of genes that exist only in cephalopods, many of which are particularly active in the brain, skin and suckers; that is, in the main organs whose peculiarity has to find an explanation.

"The octopus looks completely different from all other animals," says co-leader of the research Clifton Ragsdale, of Chicago, "and even the rest of molluscs, of which it is distinguished by its eight prehensile paws, his big brain and his intelligent problem-solving skills, the late British zoologist Martin Wells said” the octopus is an alien, in this sense, then, our article describes the first sequenced genome of an alien. "

Octopus evolutionary lineage dates back to 500 million years ago, almost to the origin of the animals as a whole. Consequence of that age, and a high capacity to adapt to change, the different species of octopus now dwell in all oceans almost any depth. They are certainly the most intelligent invertebrates. And they have 33,000 genes, compared to 20,000 of our species.

The main evolutionary vector of the extraordinary capabilities of octopus was probably the serial duplication of a few critical genes. It highlights a particularly brutal amplification of genes protocadherins, a family of essential proteins in regulating nervous system development, and interactions between neighboring neurons. Vertebrates have also expanded greatly this gene, although independently of the octopus family. In fact, until now we believed that the explosion of these genes was one of the main explanations for our superiority among creatures of evolution. And wait for the next genome. Octopuses, squid and cuttlefish, a group of mollusks are known as champions cefalópodos- camouflage in the ocean. The octopus can mimic the color and texture of a rock or a piece of coral. The squid can brighten your skin to resemble the water in which they swim. And cuttlefish can even be covered with black and white squares if a scientist gets a chessboard in your aquarium.

Cephalopods can do these shows thanks to a dense network of specialized cells that are on the skin. But before you can take a new guise, they should receive the fund that want to merge.

Cephalopods have big, powerful eyes to capture their environment. But two new studies published by   The Journal of Experimental Biology   They indicate that they have another way to sense light: the skin. It is possible that these animals have developed an eye that occupies your entire body.

When light enters the eye of a cephalopod, it crashes against retinal molecules called opsins. The collision triggers a biochemical reaction that sends an electrical signal from the eye to the brain cephalopod (we also generate a similar form of opsins in the eyes).

The skin of cephalopods contains a pigment-filled cells called chromatophores

In 2010, Roger T. Hanlon, a biologist at the Marine Biological Laboratory in Woods Hole, Massachusetts, and his colleagues claimed that opsins cuttlefish also made ​​in the skin . This discovery raised the tantalizing possibility that animals could use the skin to sense light as much as they do their eyes. Hanlon joined Thomas W. Cronin, visual ecologist at the University of Maryland in Baltimore County, and his colleagues to study it more closely.

The skin of cephalopods contains a pigment-filled cells known as chromatophores, which are surrounded by muscles and nerve endings. When the muscles contract, extend the chromatophores, which allows them to absorb more light and gives new colors to the animals. Cephalopods have chromatophores to 16,000 per square centimeter of skin, which they use as a kind of screen HD video.

Hanlon, Cronin and his colleagues developed precise molecular probes that could be used to locate the opsins in the skin.   They found that, cuttlefish,   opsins occur only in chromatophores. So was the calamari.Similarly, scientists   They discovered other enzymes in the skin of animals that are present in the eye, which allow opsins transmit light signals to the nervous system.

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These studies convinced scientists that the cephalopods could have developed a system to perceive light, and perhaps the color, directly through the skin. Then they removed pieces of animal skin and lit to see if they could get an answer.

For more times they tried, they failed. But two other scientists were luckier. Hanlon study inspired Todd H. Oakley, a biologist at the University of California, Santa Barbara, and Desmond M. Ramirez, a graduate student, to join the search for skin opsins. Instead of squid or cuttlefish, octopus decided to study, they collected marsh located near the campus.

The scientists found that octopuses, like cuttlefish, have opsins in the skin. But instead of producing them in chromatophores, octopuses just made ​​opsins in a hair-like nerve endings that occur in the skin.

Oakley Ramirez and skin fragments cut octopus to check whether they respond to light. When scientists left dark skin or subjected to a dim red light, he remained pale. But when the light lit, the chromatophores were expanding rapidly, darkening the skin in seconds.

"We did not expect such a quick reaction," says Oakley, who suspects that light impacts skin opsins, which stimulate neurons to transmit information to neighboring chromatophores. Oakley Ramirez and skin exposed to light of various colors to test your sensitivity. The blue light was triggering the fastest response. Opsins octopus eye are also particularly sensitive to such light.

"I am very happy that I have achieved," says Hanlon on studies of Oakley and Ramirez. "And I feel a little envious," he adds. Their findings have encouraged try again. Although it succeeds with cuttlefish and squid, yet no one can say exactly how animals use the light they capture opsins to control their skin color. "It's a very strange story," says Hanlon, "but our animals are also"

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