In a first, researchers at the Tel Aviv University have discovered an animal that does not require oxygen to survive. The parasite lives in salmon tissue and is believed to be a relative of the jellyfish. As the animal evolved, it gave up breathing and consuming oxygen to produce energy. The H. salminicola "steals ready-made nutrients" from salmon, inside which it lives. A study related to the discovery was published in the journal PNAS and expands the definition of what an animal could be.