No Oxygen Needed

Even the most fundamental biological theories can be shown to be incorrect or at the very least uncomplete. That was demonstrated by researchers from Tel Aviv University in 2020, when they unintentionally found the first animal to survive without oxygen.

The in question organism is a whitish parasite with an 8-millimeter diameter known as Henneguya salminicola. It affixes to a wide range of salmon species and spreads a disease called "milky meat" or "tapioca." Although this parasite has been well known for more than a century, it wasn't until researchers mapped the genome of the Henneguya genus that they realized H. salminicola lacked the mitochondria necessary for aerobic respiration.

In fact, the parasite lacked any mitochondrial DNA, suggesting that it had somehow evolved to generate energy devoid of oxygen, albeit the specifics of how it does this are yet unknown. This is something that other creatures like amoebas and fungi can do, but H. salminicola is the first example of what may be considered a "animal" missing aerobic respiration.