Anaerobic animal excites scientists
Scientists have discovered a non-oxygen breathing animal, shaking up long-held assumptions about life on Earth.
Researchers at Tel Aviv University (TAU) have discovered a less than 10-celled parasite Henneguya salminicola lives in salmon muscle. As it evolved, the animal appears to have given up breathing and consuming oxygen to produce energy.
“Aerobic respiration was thought to be ubiquitous in animals, but now we confirmed that this is not the case,” Professor Dorothee Huchon explains.
“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.”
Some other organisms like fungi, amoebas or ciliates in anaerobic environments have lost the ability to breathe over time. The new study demonstrates that the same can happen to an animal -- possibly because the parasite happens to live in an anaerobic environment.
The parasite's anaerobic nature was an accidental discovery. While assembling the Henneguya genome, Prof Huchon found that it did not include a mitochondrial genome.
The mitochondria is the well-known ‘powerhouse of the cell’, where oxygen is captured to make energy, so its absence indicates that the animal does not breathe oxygen.
Until the new discovery, there was debate regarding the possibility that organisms belonging to the animal kingdom could survive in anaerobic environments.
The assumption that all animals are breathing oxygen was based, among other things, on the fact that animals are multicellular, highly developed organisms, which first appeared on Earth when oxygen levels rose.
“It's not yet clear to us how the parasite generates energy,” Prof Huchon says.
“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 characterises anaerobic non-animal organisms.”
The discovery bears enormous significance for evolutionary research.
“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,” she 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.”