Until now, it had generally been assumed that all animals breathe oxygen. According to Israeli scientists, however, that isn't the case – they've announced that a tiny relative of jellyfish and corals manages to get by without.
The discovery was initially made by Tel Aviv University's Prof. Dorothee Huchon, when she realized that a microscopic fish parasite known as Henneguya salminicola lacked a mitochondrial genome. Found in large numbers in most cells, the mitochondria are organelles that capture oxygen in order to produce energy. Because these are lacking in the parasite, Huchon and colleagues determined that it must not be an oxygen-breather.
While organisms such as fungi and amoebas also don't breathe oxygen, this is reportedly the first time that it's been noted in an actual animal – Henneguya does in fact qualify as an animal, even though it's made up of fewer than 10 cells. Its unique adaptation could likely be due to the fact that the creature lives in the muscles of salmon, where oxygen is in short supply during anaerobic activity.
That said, it still isn't clear how the parasite does make do. The researchers believe that it may draw energy from the surrounding salmon cells, or that it might utilize a different type of respiration such as oxygen-free breathing. In any case, the discovery has definitely caused the scientists to rethink some things.
"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," says Huchon. "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."
A paper on the research was recently published in the journal PNAS.
Source: American Friends of Tel Aviv University