This is rather cool:
BBC News - First oxygen-free animals foundScientists have found the first animals that can survive and reproduce entirely without oxygen, deep on the floor of the Mediterranean Sea.
He told BBC World Service they were about a millimetre in size and looked like jellyfish in a protective shell.
The basin, 200km (124m) off the western coast of Crete, is about 3.5km (2.2m) deep and is almost entirely depleted of oxygen, or anoxic.
Considering the implications of creatures which can exist without oxygen, she said that greater study of animal-microbe interactions in the extreme environment of Earth's oceans could help answer questions about the possibility of life existing on other planets with different atmospheres.