A group of researchers led by Dayana Yahalomi from Tel Aviv University (Israel) found that the creature Henneguya salminicola has a complete absence of the mitochondrial genome. This means that he not only does not have mitochondria in his cells, but he also does not know how to create them - the corresponding information is simply absent in his genome. This is a paradox - it is thanks to mitochondria that all living things use oxygen for life, and nothing else.
The test organism is classified as cnidarians or stinging, it looks like a tiny jellyfish and is a parasite of salmon. To study it, Israeli scientists used deep sequencing and fluorescence microscopy, the data of which were then double-checked for another parasite, Myxobolus squamalis. His mitochondrial genome was identified quite accurately and clearly, so there is no need to talk about an error with Henneguya salminicola. It turns out that before scientists - the first living creature in the world that relies in its life only on anaerobic processes.
Similar creatures have been known for a long time, but they are all the simplest unicellular organisms, and here is a rather complex multicellular organism. And this is not an alien from space - on the contrary, the living conditions of the parasite inside the host's body, in an extremely oxygen-poor environment, contribute to the evolutionary development of anaerobic metabolism. Its ancestors were advanced jellyfish, but the parasite degraded to a simpler creature, losing important genes and adapting to a new environment.
Scientists honestly admit that they do not yet understand how this parasite survives if it does not use oxygen to create the ATP molecule, which is involved in many intracellular processes. Maybe it gets ready-made from the host's organism? In any case, this is a great example of how interesting and unpredictable evolution can take. And how little we still know about life, even on our home planet.