A very weird news item: multicellular organisms that appear to be able to live without oxygen. They're part of the little-known (and only recently codified) phylum Loricifera, and these particular organisms were collected at the bottom of the Mediterranean, in a cold, anoxic, hypersaline environment.

They have no mitochondria - after all, they don't have any oxygen to work with. Instead, they have what look like hydrogenosome organelles, producing hydrogen gas and ATP from pyruvate. I'm not sure how large an organism you can run off that sort of power source, since it looks like you only get one ATP per pyruvate (as opposed to two via the Krebs cycle), but the upper limit has just been pushed past a significant point.