10 animals that can survive without oxygen for long periods

Humans start suffering brain damage after just a few minutes without oxygen. But across the animal kingdom, evolution has produced a small, remarkable group of creatures that can shut down their need for air entirely, sometimes for days, sometimes for months, and in a few extreme cases, for years. From frozen ponds in Siberia to the bottom of the Mediterranean Sea, these animals have found ways to survive in conditions that would kill almost anything else. Here are ten of the most extraordinary examples.

Painted Turtles and Pond Sliders

North American freshwater turtles in the genera Trachemys and Chrysemys, commonly known as painted turtles and pond sliders, are considered the most anoxia-tolerant vertebrates ever studied. When ice locks over their ponds in winter, these turtles bury themselves in mud and switch entirely to anaerobic metabolism. Research shows they can survive without any oxygen for up to two weeks at around 16 degrees Celsius and an astonishing 12 to 18 weeks at colder temperatures near freezing. They manage this by tolerating levels of lactic acid buildup that would be lethal to almost any other vertebrate, while dramatically slowing their metabolic rate to conserve energy until spring thaw.

The Ocean Quahog

Arctica islandica, better known as the ocean quahog, is not just one of the most oxygen-deprivation-tolerant animals alive; it is also the longest-living non-colonial animal on Earth, with individuals recorded living beyond 400 years. This clam can survive extended periods without oxygen, with roughly half of a tested population still alive after 55 days of total anoxia. It achieves this by burrowing into the seabed, sealing its shell shut, and dropping its metabolic activity to as little as one per cent of normal, a strategy scientists believe may also be linked to its extraordinary lifespan.

Naked Mole-Rats

Naked mole-rats are already famous for their resistance to cancer and pain, but their tolerance for low oxygen is just as striking. Living in crowded underground burrows where oxygen is scarce and carbon dioxide builds up, these rodents have evolved the ability to survive up to eighteen minutes with zero oxygen, without any lasting damage to their brains or organs. Where ordinary mice die within twenty seconds in the same conditions, naked mole-rats simply switch their bodies over to a fructose-driven metabolic pathway, essentially running on a sugar reserved for emergencies, until air returns.

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The Siberian Wood Frog

The Siberian wood frog, Rana amurensis, has colonised some of the coldest, most oxygen-starved waters on the planet, including areas as far north as 71 degrees latitude. During winter, the lakes and rivers it overwinters in can become almost completely oxygen-free beneath thick ice, a condition that kills most fish and amphibians outright. This frog, however, has adapted to survive months underwater in these severely hypoxic and even fully anoxic conditions, a feat that has helped it thrive in parts of Northern Asia where competing amphibian species simply cannot survive.

Crucian Carp and Goldfish

Crucian carp, along with their close relatives goldfish, have developed one of the most unusual survival tricks in the animal kingdom. Trapped under ice in northern European and Asian ponds for months at a time, they cannot rely on the lactic acid buildup that limits most anaerobic animals. Instead, their bodies convert carbohydrates into ethanol, essentially alcohol, which is then released harmlessly through their gills. This biochemical workaround allows them to go up to five months without breathing any oxygen at all, an ability unmatched by nearly any other vertebrate.

Tardigrades

Tardigrades, the microscopic water-dwelling animals often called water bears, are best known for surviving extreme drying and even the vacuum of space. Less well known is their ability to enter a state called anoxybiosis when oxygen disappears from their environment. In this suspended state, metabolic activity drops to near-undetectable levels, allowing them to wait out periods of severe oxygen deprivation before resuming normal activity once conditions improve, one more entry in a long list of survival tricks that make tardigrades among the toughest animals ever studied.

Brine Shrimp

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Brine shrimp, of the genus Artemia, produce encysted embryos that rank among the most stress-resistant biological structures known to science. When conditions turn harsh, adult brine shrimp release these cysts instead of live young, and the embryos inside arrest their development completely, shutting down nucleic acid and protein synthesis. In this dormant state, cysts can withstand total anoxia for months or years, with some records showing viable hatching after roughly 250 years in storage, alongside tolerance for extreme radiation, temperature swings, and even exposure to the vacuum of space.

Henneguya Salminicola

This tiny parasite, which lives inside the muscle tissue of salmon, made headlines as the first known multicellular animal that does not breathe oxygen at all. Related to jellyfish and coral, Henneguya salminicola has fewer than ten cells and, over the course of its evolution, lost the mitochondrial genome that most animals rely on for aerobic respiration entirely. Researchers at Tel Aviv University who identified the trait described it as proof that evolution can abandon even the most fundamental biological processes when an anaerobic environment makes it unnecessary.

Loriciferans

Discovered in hypersaline, oxygen-free mud more than 10,000 feet deep in the Mediterranean Sea, loriciferans became the first multicellular animals ever confirmed to live their entire lives without oxygen. These jellyfish-like creatures, measuring less than a millimetre long, lack mitochondria altogether and instead rely on organelles resembling hydrogenosomes, an anaerobic energy-producing structure previously seen only in single-celled organisms. Some of the specimens recovered even contained eggs, confirming they were not simply washed down from oxygenated waters above but were living and reproducing in total anoxia.

Freshwater Turtles in Deep Winter Dormancy

Beyond the general resilience of the Trachemys and Chrysemys genera, certain overwintering turtle populations demonstrate an additional survival mechanism worth highlighting on its own: extrapulmonary oxygen uptake, where limited gas exchange occurs through skin and other tissue surfaces even while lungs are effectively useless underwater. Combined with severe hypometabolism, this allows some turtle populations to stretch survival windows even further during unusually long, harsh winters, underscoring just how many overlapping adaptations nature has stacked onto a single group of animals to guarantee their survival through the coldest, most oxygen-starved months of the year.