Oxygen is very important for life on Earth. We breathe it in, our cells live, and without oxygen we will die instantly. All multicellular life on Earth has evolved using oxygen over millions of years.
But take a deep breath, because we need to talk about Henneguya salminicola, a tiny parasite with fewer than 10 cells that lives in the muscle tissue of salmon. The tadpole-like parasite doesn't do trivial things like breathing. No, it looks like H. salminicola is the first multicellular animal we've found that doesn't need oxygen.
“Aerobic respiration was considered common in animals, but now we have confirmed that it is not,” Dorothy Hoochon, a zoologist at Tel Aviv University in Israel, said in a press release.
Hoochon and a team of international researchers examined and sequenced all the genes of H. salminicola in their study published in the National Academy of Sciences' journal Proceedings. They found that the parasite lacks the DNA machinery needed to 'breath' – it lacks mitochondria. Mitochondria are often referred to as the 'powerhouse' of the cell because they use oxygen to produce energy. It looks like a small factory inside (almost) all cells and DNA.
The discovery was accidental for the team that examined the genome of the species. When they set out in search of mitochondrial genes, they returned empty-handed.
“Our discovery shows that evolution may be going in strange directions,” Hoochon said. “Aerobic breathing is the main source of energy, and yet we found an animal that did not take this path.”
Some unicellular life forms have developed the ability to live without oxygen and also lack mitochondria. Many bacteria and protozoa can exist without oxygen at all, such as those found on the ocean floor near hydrothermal vents and some human pathogens that live inside the body. Instead of oxygen, they get energy from fermentation or use other molecules like mercury or iron.
But how H. salminicola generates energy is still unclear. Hoochon speculates that the parasite could get oxygen from salmon cells or could develop methods similar to those that scientists have documented in the past.
Sources: Photo: Stephen Douglas Atkinson
