Researchers have discovered the only animal in the world that does not need oxygen to survive. It turned out to be a common salmon parasite. A study published in the National Academy of Sciences journal Proceedings showed that the parasite Henneguya salminicola does not require breathing to survive – a revelation that can change the understanding of life on Earth and beyond. The study's authors write that a multicellular organism that is part of a group of animals closely associated with jellyfish known as Myxozoa does not breathe at all and does not have mitochondrial DNA. But how is that possible?
This is the first multicellular animal in the wild, in whose DNA no genes are responsible for breathing. According to the results, the parasite has "lost the ability to breathe aerobically". At the start of a study in 2010, scientists suggested that the Lorifer species, another microscopic animal, could survive without oxygen, although according to the BBC, this finding has not been fully confirmed.
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No matter how surprising this discovery may seem to us, Henneguya salminicola is a fairly common organism that parasitizes salmonids and causes disease in them. Some diseases lead to the appearance of ugly cysts on salmon meat, but are usually harmless to humans and the fish themselves. Because Henneguya salminicola is a parasite in fish, this tiny creature has evolved to survive in conditions where oxygenation is irregular. According to the authors of the study, almost all multicellular organisms, including plants and fungi, cannot survive without oxygen. During evolution, Henneguya salminicola not only lost some of the genes that are directly related to aerobic respiration, but also invented a method for the oxygen-free breakdown of essential nutrients.
As co-author of the study, evolutionary biologist at the University of Tel Aviv, Dorote Yushon, told Live Science that these tiny parasites had lost tissue, nerve cells, muscles, and everything else, including their breathability. The question of how Henneguya salminicola can survive without oxygen remains unanswered. Researchers believe the parasite can drain energy from its host.
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The entire set of genes associated with the work of mitochondria in DNA – organelles the size of a bacterium – is completely absent from the Henneguya salminicola parasite. Instead, the animal relies on a chain of genes that allow it to break down the necessary sugar from mitochondria without enzymes, as is normally the case with other organisms. However, scientists still have to learn exactly how the metabolism of this truly unique organism works.
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And yet scientists can tell something interesting about Henneguya salminicola today. So the set of genes revealed in the parasite is unique – it is completely different from the DNA chains that are characteristic of eukaryotes – the type of organism that consists of several cells – and other organisms that do not require oxygen. Scientists hope that further studies on the salmon parasite will not only produce drugs that rid the fish of parasites, but will also help us to learn more about life forms that are completely unknown to us.