The common concept that all organisms need oxygen to live might be wrong as researchers discovered a unique organism that does not need to breathe to survive. This jellyfish-like parasite is the first multicellular organism known that does not have a mitochondrial genome, therefore, living its life without depending on oxygen.

This new discovery changes the definition of what an animal can be and can have implications on the search for an extraterrestrial life.

This tiny parasite survived in salmon tissue and evolved so that it does not need oxygen to produce energy. It is a great simplification that sometimes less is more, according to Stephen Atkinson, a senior research associate at the Department of Microbiology at Oregon State University.

The Beginning of Life

Over 1.45 billion years ago, life started to develop the ability to metabolize oxygen or to respirate. A larger archaeon and a smaller bacterium developed a symbiotic relationship when the archaeon engulfed the bacterium and discovered that their relationship has become beneficial to both of them.

Eventually, their relationship resulted in the two organisms evolving together, and those bacteria concealed inside became the mitochondria - an organelle essential for energy production in a cell. It plays a vital role in the respiration process and can be found in large numbers in every cell of the body except for red blood cells.

They convert oxygen and nutrients into a molecule called adenosine triphosphate (ATP) that powers the cell's metabolic processes.

Although some organisms have adapted to thrive in a low-oxygen or hypoxic environment, with some single-celled organisms that have even developed mitochondria-related organelles for anaerobic metabolism, it has been a subject of scientific discussions whether there is a possibility of an exclusively anaerobic multicellular organism.

It is not until researchers from Tel Aviv University in Israel, led by Dayana Yahalomi, discovered something unusual on the common salmon parasite called Henneguya salminicola, that they found the answer to their question.

How Did the Parasites Survive in a Hypoxic Environment?

This parasite is a cnidarian, which belongs to the same phylum as the corals, jellyfish, and anemones. They live their entire life cycle inside the salmon and steals ready-made nutrients instead of consuming oxygen on its own, and they are not harmful to humans even though they create unsightly cysts in the salmon's flesh.

They can survive hypoxic environments inside its host, which baffled scientists. Atkinson, who co-authored the paper, said that when thinking about animals we picture a multicellular organism that requires oxygen to survive, but with the case of the parasite, there is at least one multicellular animal that does not have the genetic toolkit to use oxygen.

The researchers used deep sequencing and fluorescence microscopy in studying the H. salminicola, and they found that it lost its mitochondrial genome, it's capacity for respiration, and that they have developed folds in the inner membrane not usually seen.

Although they lost most of their original jellyfish genome, they also retained an oddly complex structure that looks like jellyfish stinging cells to cling to their hosts-they are the structures that look like eyes.

This research could help fisheries adapt their techniques in rearing salmon to deal with the parasite as no one wants to buy a salmon riddled with tiny weird jellyfish no matter how harmless they are.