This animal doesn’t need oxygen to survive

Hyperaxion Feb 25, 2020

To the surprise of scientists, a parasite that lives in the muscles of salmon does not have mitochondria, part of the cell essential to capture oxygen and generate energy.

Researchers at Tel Aviv University have made a discovery that changes some of the most basic precepts about the animal kingdom.

Published in the scientific journal PNAS, the study led by biologist Dorothee Huchon reveals that Henneguya salminicola, a parasite that lives in the muscles of salmon, can survive without breathing oxygen.

No mitochondria

The discovery was made while the researchers were sequencing the genome of parasites of the class Myxozoa, of which H. salminicola is part.

That was how the team noticed that this small organism, with less than 10 cells, did not have mitochondrial material.

The mitochondria is the part of the cell responsible for capturing oxygen to generate energy. Its absence indicates that the animal is not breathing this gas.

Survival guide

Although it is not yet clear to experts, they believe that this behavior of Henneguya salminicola is because the tiny animal has adapted very well to the environment in which it lives, which is anaerobic, that is, it does not have oxygen.

What is still speculated is how the parasite manages to generate its own energy. “It may be extracting from the surrounding fish cells or it may have a different type of breathing, such as oxygen-free breathing,” suggests Huchon.

“Evolution can take strange directions”

This animal doesn't need oxygen to survive
Henneguya salminicola, the first animal discovered that does not need to breathe oxygen to survive. (Source: Tel Aviv University).

Until the publication of the article, it was believed that aerobic respiration was ubiquitous in animals. “Now we confirm this is not the case,” says the researcher. “Our discovery shows that evolution can take strange directions.

Aerobic breathing is an important source of energy, and yet we found an animal that abandoned that path.”


According to the biologist, this finding has enormous significance for studies on the evolutionary process.

“Generally, it is thought that, during evolution, organisms become increasingly complex and that single-celled organisms are the ancestors of complex organisms,” she explains.

“But here, right in front of us, there is an animal whose evolutionary process is the opposite. Living in an oxygen-free environment, it disposed of unnecessary genes responsible for aerobic respiration and became an even simpler organism.”

This has never been observed in the animal kingdom before

The ability to survive without oxygen had already been observed in the Fungi and Protista kingdoms, which include organisms such as fungi, amoebas and ciliate strains, but never in the animal kingdom.

At first, until the publication of this research, scientists assumed that animals breathed only with the presence of oxygen because they are multicellular organisms, highly developed and that appeared on the planet only after the increase of oxygen in our atmosphere.


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