Scientists have discovered a non-oxygen breathing animal, a tiny, less than 10-celled parasite named
Henneguya salminicola which lives in salmon muscle.
As it evolved, the animal, a myxozoan relative of jellyfish and corals, gave up breathing and consuming oxygen to produce energy.
Aerobic respiration is a major source of energy but organisms like fungi, amoebas or ciliate lineages in anaerobic environments have lost the ability to breathe over time. This is
the first discovery of an animal that gave up this critical pathway, possibly because the parasite happens to live in an anaerobic environment.