This is pretty neat: scientists have apparently discovered the first example of truly anaerobic animal life (i.e. an animal that can survive in the absence of oxygen). This isn’t some sort of fuzzy critter, though; instead, these are tiny (less than 1 mm in length) animals that were found on the floor of the Mediterranean Sea. The animals belong to the phylum Loricifera (see illustration below). Significantly, these animals lack mitochondria, the sub-cellular organelles where oxygen is employed to produce ATP in aerobic (oxygen-dependent) life.
Danovaro, R., Dell’Anno, A., Pusceddu, A., Gambi, C., Heiner, I., & Kristensen, R. (2010). The first metazoa living in permanently anoxic conditions BMC Biology, 8 (1) DOI: 10.1186/1741-7007-8-30
Levin, L. (2010). Anaerobic Metazoans: No longer an oxymoron BMC Biology, 8 (1) DOI: 10.1186/1741-7007-8-31
Mentel, M., & Martin, W. (2010). Anaerobic animals from an ancient, anoxic ecological niche BMC Biology, 8 (1) DOI: 10.1186/1741-7007-8-32