[Slashdot] - Scientists Find the First-Ever Animal That Doesn't Need Oxygen To Survive

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Scientists from Tel Aviv University in Israel discovered that a salmon parasite called Henneguya salminicola doesn't have a mitochondrial genome -- the first multicellular organism known to have this absence. That means it doesn't breathe; in fact, it lives its life completely free of oxygen dependency. ScienceAlert reports: It's a cnidarian, belonging to the same phylum as corals, jellyfish and anemones. Although the cysts it creates in the fish's flesh are unsightly, the parasites are not harmful, and will live with the salmon for its entire life cycle. Tucked away inside its host, the tiny cnidarian can survive quite hypoxic conditions. But exactly how it does so is difficult to know without looking at the creature's DNA -- so that's what the researchers did. They used deep sequencing and fluorescence microscopy to conduct a close study of H. salminicola, and found that it has lost its mitochondrial genome. In addition, it's also lost the capacity for aerobic respiration, and almost all of the nuclear genes involved in transcribing and replicating mitochondria. Like the single-celled organisms, it had evolved mitochondria-related organelles, but these are unusual too -- they have folds in the inner membrane not usually seen. The same sequencing and microscopic methods in a closely related cnidarian fish parasite, Myxobolus squamalis, was used as a control, and clearly showed a mitochondrial genome. These results show that here, at last, is a multicellular organism that doesn't need oxygen to survive. Exactly how it survives is still something of a mystery. It could be leeching adenosine triphosphate from its host, but that's yet to be determined. But the loss is pretty consistent with an overall trend in these creatures - one of genetic simplification. Over many, many years, they have basically devolved from a free-living jellyfish ancestor into the much more simple parasite we see today. The findings have been published in the journal PNAS.

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