Animals That Don't Need Oxygen - It Gets Weirder

"First Animals Found That Live Without Oxygen"
Wired Science (April 7, 2010)

"In the muck of the deep Mediterranean seafloor, scientists have found the first multicellular animals capable of surviving in an entirely oxygen-free environment.

"Some types of bacteria and other single-celled organisms can live without oxygen, but nothing as complex had been found as these three species of Loricifera, a group of marine-sediment dwellers who inhabit one of Earth's most extreme and little-known environments.

" 'The discovery of these life forms opens new perspectives for the study of metazoan life in habitats lacking molecular oxygen,' wrote researchers led by Roberto Danovaro, a marine biologist at Italy's Polytechnic University of Marche, in a study published April 6 in BMC Biology...."

These critters are very tiny ones. Less than a millimeter long. But they're animals. That don't need oxygen.

That isn't the weirdest thing about them, I think.

Just about every animal has mitochondria. Mitochondria convert oxygen and nutrients into energy for us. Even animals that don't have mitochondria have structures that appear to be mitochondrial parts that perform the same functions.

These new Loricifera? They don't have mitochondria. At all. Not even mitochondrial parts.

What they do have is hydrogenosomes: some single-cell creatures have them. hydrogenosomes convert energy without oxygen. Which was a vital ability around 600,000,000 years ago, when Earth didn't have oxygen in its oceans. Or atmosphere. Not enough to matter, anyway.

Oxygen was, in a way, the first serious pollutant on Earth. Judging from the fossil record, quite a few species died out when photosynthetic plants started carelessly pouring that dangerous chemical into the ecosystem.

Finding animals that don't need oxygen is big for paleontologists. As the article says:

"...The evolutionary history of these creatures is not known, but they live in an environment reminiscent of Earth's oceans some 600 million years ago, before the deep seas were oxygenated and large animals evolved, wrote Comenius University (Slovakia) biochemist Marek Mentel and Düsseldorf University (Germany) biologist William Martin in an accompanying commentary."

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