It indeed sounds like science fiction, but here it goes: it has fewer than 10 cells, lives within a salmon’s muscles and mitochondria is nowhere to be found.

What this means is that Tel Aviv University scientists have discovered the first-ever multicellular animal that doesn’t need oxygen to survive, according to a study published in the journal Proceedings of the National Academy of Sciences.

This petite parasite, known as Henneguya salminicola, doesn’t possess the capability to breathe even if it wanted to, as it jettisoned that process long ago as it evolved.

The parasite, a distant relative of jellyfish and corals, is relatively harmless even though it lives within the muscle tissues of salmon. Henneguya salminicola can’t infect humans, but can cause “milky flesh” or “tapioca” disease, which is responsible for white liquid-filled cysts on the fish, according to the Alaska Department of Fish and Game.

The scientists accidentally made this remarkable finding while sequencing the Henneguya genome. They were surprised to discover that Henneguya salminicola doesn’t have any genes for mitochondria, which is known to produce energy for cells via aerobic respiration.

The researchers, however, are still stumped in trying to understand exactly how the parasite produces energy.

“It’s not yet clear to us how the parasite generates energy,” Tel Aviv University professor and lead author Dorothee Huchon said in a press release.

“It may be drawing it from the surrounding fish cells, or it may have a different type of respiration such as oxygen-free breathing, which typically characterizes anaerobic non-animal organisms.”

The discovery of Henneguya salminicola has opened up new possibilities on how life evolved on planet Earth.

“Aerobic respiration was thought to be ubiquitous in animals, but now we confirmed that this is not the case,” Huchon said. “Our discovery shows that evolution can go in strange directions. Aerobic respiration is a major source of energy, and yet we found an animal that gave up this critical pathway.”

This parasite also proves that life doesn’t always follow a linear path toward increased complexity.

“It is generally thought that during evolution, organisms become more and more complex, and that simple single-celled or few-celled organisms are the ancestors of complex organisms,” Huchon said.

“But here, right before us, is an animal whose evolutionary process is the opposite. Living in an oxygen-free environment, it has shed unnecessary genes responsible for aerobic respiration and become an even simpler organism.”

Ethen Kim Lieser is a Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek and Arirang TV. He currently resides in Minneapolis.

Image: Reuters