Breathing oxygen is considered a fundamental characteristic of multicellular animals, but scientists have found at least one that can’t do it.
Scientists have just discovered a jellyfish-like parasite does not have a mitochondrial genome – the first multicellular organism known to have this absence. This means it doesn’t breathe; in fact, it lives its life completely free of oxygen dependency.
This theory not just changes our understanding of life here on Earth, it could shed some light on how alien life could exist on other planets.
Researchers at Tel Aviv University say the jellyfish-like parasite spends its life clinging to the inside of a salmon in a low to zero oxygen environment.
“They have lost their tissue, their nerve cells, their muscles, everything,” study co-author Dorothée Huchon, an evolutionary biologist at Tel Aviv University in Israel, told Live Science. “And now we find they have lost their ability to breathe.”
It was thought that all plants and animals used oxygen to generate a fuel called adenosine triphosphate (ATP), which powers cellular processes. The generation of ATP from oxygen takes place in structures called mitochondria.
Each mitochondrion has its own tiny genome, distinct from the main genome of the cell nucleus. But when Huchon and her colleagues sequenced the DNA of Henneguya salminicola, which is related to jellyfish, they thought they had made a mistake because they had found no mitochondrial DNA.
‘Our discovery confirms that adaptation to an anaerobic environment is not unique to single-celled eukaryotes, but has also evolved in a multicellular, parasitic animal,’ the researchers wrote in their paper.
‘Hence, H. salminicola provides an opportunity for understanding the evolutionary transition from an aerobic to an exclusive anaerobic metabolism.’
How exactly it survives is still a mystery for the scientists. It could be leeching adenosine triphosphate from its host, but that yet remains to be determined.
It’s not the first creature discovered that can go long periods without oxygen – but it’s the first complex organism that does not need it at all.
“Our discovery confirms that adaptation to an anaerobic environment is not unique to single-celled eukaryotes, but has also evolved in a multicellular, parasitic animal,” the researchers wrote in their paper.
“Hence, H. salminicola provides an opportunity for understanding the evolutionary transition from an aerobic to an exclusive anaerobic metabolism.”
The research has been published in the journal PNAS.