Researchers have discovered the only known animal that does not need oxygen to survive, a common parasite that largely preys on salmon.
The study, published Tuesday in the journal Proceedings of the National Academy of Sciences, found that the parasite Henneguya salminicola does not require aerobic respiration in order to survive — a revelation that may change how we understand life on Earth and beyond.
The multicellular organism, which is part of a group of animals closely related to jellyfish known as the Myxozoa, does not breathe at all and does not have mitochondrial DNA.
It's the first multicellular animal found in the wild to not have the DNA, which contains the genes responsible for respiration, and has lost "the ability to perform aerobic cellular respiration," per the study. Some single-celled organisms do not need respiration to survive.
A study published in 2010 speculated that a species of loriciferans, another microscopic animal, can survive without oxygen, though, this finding has not been fully confirmed, according to the BBC.
H. salminicola is a fairly common parasite, causing "milky flesh" or "tapioca" disease in salmon, according to a guide published by the Alaska Department of Fish and Game. "Milky flesh" disease results in unsightly cysts on the salmon's flesh but is generally harmless to humans and the fish itself.
Because H. salminicola resides inside the fish, the tiny creature has evolved to survive with inadequate oxygen supply.
Researchers found that over the course of its evolutionary process, the animal has been able to survive by eliminating so many of the traits associated with multicellular species.
"They have lost their tissue, their nerve cells, their muscles, everything," Dorothée Huchon, an evolutionary biologist at Israel's Tel Aviv University and study co-author, told Live Science. "And now we find they have lost their ability to breathe."
It remains unclear how H. salminicola survives without oxygen, but Huchon speculated to Haaretz that it may be leeching energy from its host.
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