Fish feeding on the bottom material of the Hudson River, has developed a gene that gives her immunity to the class of toxins called PCBs.
A genetic mutation allows the fish to live in the water, which is largely polluted, prohibited the use of our time, industrial himikatomi. Arctic cod (Microgadus tomcod) have become one of the most rapidly evolving species in the world.
"This is a very, very rapid evolutionary change," - said Isaac Uirdzhin, a toxicologist from the School of Medicine at New York University, who led the study. "Usually, it is believed that evolution occurs over thousands and millions of years. But in this case it is only about 20-50 generations."
The study was published in the journal Science.
PCBs, or polychlorinated biphenyls, were synthesized in 1929. They found hundreds of industrial applications, mainly as a electrical insulator. After 50 years of use, they are forbidden, but they are difficult to decomposition. Partly because of contamination with PCBs, a 300-km section of the Hudson River has become one of the largest sites participating in the national program for cleaning up toxic waste.
But the 25-centimeter Atlantic cod feel good, in spite of contamination with PCBs. The level of this chemical in the liver of fish from the river, is one of the largest of the natural world. But until now, scientists did not know how she manages to survive, because PCBs kill many other species of fish.
It was found that the fish mutated by modifying the gene that is responsible for a protein regulating the toxic effects of PCBs and other chemicals. This protein is called the aryl hydrocarbon receptor2 or AHR2.
PCBs can not bind the mutated receptor protein, which reduces the effect of chemicals on there.
This is a classic example of natural selection - fish with mutated genes have survived.
Company General Electric (GE) contaminated the Hudson River 600 tons of PCBs from 1947 to 1976, and took over most of the clean-up work on them.
After a very heated discussions that took place during the decade, GE conducted an experiment in a year producing an underwater excavation. Department of Environmental Protection evaluated the risks from rising in the process, contaminants and allowed this type of cleaning. Underwater excavation will resume this spring and will last for 6 years.
But, oddly enough, treatment can harm the cod. As the theory of evolution, genetic mutations, such as this can occur due to compromise in any other field of biology. It is possible that they are not well adapted to life without PCBs.
But in any case it will benefit the Hudson predatory fish that are not adapted to the PCB, and therefore are at risk by eating contaminated cod.