Sandwiched between 'Earliest known Led Zeppelin recording' and 'Evolutionary Psychology Bingo' on BoingBoing is A multicellular organism that lives without oxygen.
This is based on a paper in BMC Biology entitled The first metazoa living in permanently anoxic conditions.
This is the first evidence of a metazoan life cycle that is spent entirely in permanently anoxic sediments. Our findings allow us also to conclude that these metazoans live under anoxic conditions through an obligate anaerobic metabolism that is similar to that demonstrated so far only for unicellular eukaryotes. The discovery of these life forms opens new perspectives for the study of metazoan life in habitats lacking molecular oxygen.