We grow up believing oxygen is essential to life, and for most animals, that’s true. But some creatures have evolved to either do without it entirely or survive impressively long stretches without a single breath. From deep-sea dwellers to desert survivors, these species are breaking all the rules of what life typically needs to keep going. Here are 12 animals that can survive with little or no oxygen, and how they manage it.
Henneguya salminicola
This strange little parasite lives in the muscles of salmon and is the first known animal that doesn’t require oxygen to survive. It’s lost its ability to perform aerobic respiration altogether, meaning it doesn’t even have mitochondria—the part of the cell that usually processes oxygen.
Instead, it relies on other energy-producing pathways to keep itself going. It’s not winning any beauty contests, but this jelly-like creature proves that even multicellular animals can survive in completely anaerobic environments.
Loricifera
These microscopic animals were discovered in the oxygen-deprived depths of the Mediterranean Sea. What makes them special is that they’ve adapted to live entirely without oxygen, using organelles called hydrogenosomes instead of mitochondria. That makes them one of the only known animals to thrive in completely anoxic environments. Their existence even suggests that early animal life might have evolved without oxygen in the first place.
Crucian carp
This humble freshwater fish might not look like a survivalist, but it has an extraordinary trick. In the winter, when lakes freeze over and oxygen levels plummet, the crucian carp switches its metabolism to produce ethanol—yes, actual alcohol—instead of relying on oxygen. That ethanol gets released through its gills, allowing the fish to survive in completely anoxic conditions for months. It’s one of the only vertebrates known to use this unusual metabolic strategy.
Naked mole-rat
These odd little rodents live in low-oxygen underground burrows and have evolved to survive without oxygen for up to 18 minutes. When oxygen runs out, they switch from using glucose to fructose to fuel their bodies—a unique trick in mammals. Scientists are fascinated by their resilience because understanding it could help us develop better treatments for heart attacks and strokes, where oxygen flow to the brain is disrupted.
Epaulette shark
Found in Australian reefs, the epaulette shark is known for surviving in shallow pools that often become oxygen-starved when the tide goes out. Rather than panic, this shark simply slows its heart rate and conserves energy until oxygen returns. It can survive up to an hour without oxygen and even longer in low-oxygen environments. It’s a quiet superhero of the sea, managing extreme stress with calm efficiency.
Vampire squid
Despite its creepy name, the vampire squid is more of a chill deep-sea drifter than a hunter. It lives in oxygen minimum zones where most creatures wouldn’t last long, but it’s got blood adapted to bind oxygen efficiently, and a metabolism that’s ridiculously slow. This combo lets it survive where oxygen levels are as low as 3%, a space so hostile most marine life avoids it entirely. The vampire squid doesn’t just endure it—it thrives there.
Halicephalobus mephisto (Devil worm)
This tiny nematode lives in water trapped a few kilometres below the Earth’s surface, where oxygen is almost nonexistent. It survives using altered enzymes and thrives in heat and pressure that would kill most other animals. Nicknamed the “devil worm,” it’s one of the deepest-living animals ever discovered. It’s a prime example of how adaptable life can be, even in the strangest corners of the planet.
Methanogenic archaea
While not technically animals, these ancient microbes deserve a mention. They produce energy by generating methane instead of using oxygen, and they’re found in some of the harshest environments—like the guts of cows, deep ocean vents, and even permafrost. They’ve been around for billions of years, and some scientists believe they could offer clues about what life might look like on other planets. If anything survives without oxygen, it’s these guys.
Desert pupfish
This little fish lives in harsh, fluctuating desert pools and has an amazing tolerance for low oxygen. When conditions get rough, it can switch to an anaerobic metabolism, letting it survive several hours in water with almost no oxygen at all. Considering how fragile fish are typically thought to be, this desert dweller flips that assumption on its head. It’s tough, scrappy, and ready for whatever the environment throws at it.
Hydra
These freshwater creatures, related to jellyfish, can survive in low-oxygen environments by slowing their metabolism and switching to anaerobic pathways temporarily. They’re small, simple, and surprisingly durable. Scientists have even studied them for clues to longevity and regeneration. While they can breathe oxygen, they don’t panic if it disappears for a little while—they just adapt quietly.
Yeast and certain bacteria
Not animals, but worth mentioning—yeast and some bacteria are masters of anaerobic respiration. Yeast famously produces alcohol and carbon dioxide without needing oxygen, which is exactly how bread rises and beer brews. These single-celled organisms are proof that life without oxygen is possible, ancient, and surprisingly useful to us humans in everyday ways.
Anaerobic parasites
Some parasites, like those in the gut or tissues of other animals, have completely ditched oxygen-based respiration. They survive just fine in oxygen-poor environments by feeding off their hosts and using alternative energy pathways. These organisms show how certain lifeforms go the route of simplification, ditching oxygen entirely in favour of a parasitic but efficient existence. It’s not pretty, but it works.