Israeli researchers say they’ve discovered the first animal on earth that appears to survive without the use of oxygen.
Scientists at Tel Aviv University studying a tiny parasite related to jellyfish that lives inside salmon were surprised to discover it does not have the necessary systems to process oxygen — which were hitherto thought to exist in all multi-cellular lifeforms.
The parasite, Henneguya salminicola, lives in the muscle cells of fish, an anaerobic — or oxygen-free — environment. Researchers at TAU’s School of Zoology mapped the creatures’ genome to try and understand how it survives in such conditions, only to discover its cells lack mitochondria.
Mitochondria is an organelle present in the cells of multi-cellular creatures which is often described as the cell’s power plant. It converts oxygen to the chemical energy needed to power the cell. Aerobic respiration is impossible without it.
The researchers said H. salminicola‘s genome structure did indicate it once possessed mitochondria, but lost the organelle over time.
“Aerobic respiration was thought to be ubiquitous in animals, but now we confirmed that this is not the case,” TAU’s Prof. Dorothee Huchon, who led the study, 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.”
The study was published Monday in prominent scientific journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).
“It’s not yet clear to us how the parasite generates energy,” Huchon said. “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.”
She added: “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.
“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.”