Evolution: a multicellular animal needs no oxygen (Evolution)

by David Turell , Monday, February 24, 2020, 21:50 (1516 days ago) @ David Turell

Newly found, with no explanation as to why it is different:

https://www.newscientist.com/article/2235009-animal-that-doesnt-need-oxygen-to-survive-...

“'It has lost the ability to breathe oxygen,” says Dorothee Huchon at Tel Aviv University in Israel. It remains a mystery how this animal, a parasite that infects salmon, gets the energy it needs without oxygen, she says, but it most likely steals it from its host.

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"Each mitochondrion has its own tiny genome in addition to the main genome in the cell nucleus. But when Huchon’s team sequenced the DNA of Henneguya salminicola, which is related to jellyfish, they thought they had made a mistake because they found no mitochondrial DNA at all.

"Further studies confirmed the finding. When the team stained H. salminicola with a blue fluorescent dye that binds to DNA, no DNA was visible in cells outside the nucleus. By contrast, when they stained a closely related parasite, blue dots corresponding to mitochondrial genomes were visible outside the nucleus.

"So while the cells of H. salminicola have structures that look like mitochondria, they cannot make the enzymes needed to use oxygen to produce ATP. “These are not true mitochondria,” says Huchon.

"This means H. salminicola is a multicellular animal that can survive entirely without oxygen. “There are plenty that can go for extended periods without, but nothing that can get through the whole life cycle,” says Nick Lane of University College London.

"We don’t know why H. salminicola has lost this ability while all of its immediate relatives that we have identified use oxygen. As these parasites move through their life cycle, they may also live inside a worm host where they would have to make do with virtually no oxygen, as well. The worm host of H. salminicola has never been identified, but it too may live in sediments with very low oxygen levels, Huchon says.

"Although the parasite is harmless to humans, it is a major problem for fish farmers because it creates unsightly white spots in the flesh of infected fish."

Comment: Very unusual branch of evolution. Perhaps the host worm gives it a little oxygen. But it fits into its necessary econiche