List of Animals That Can Live Without Oxygen

Oxygen is considered essential for life on Earth, as most living organisms depend on it to produce energy and survive.

However, the way nature works is much more complex and adaptable than we might think. Through research, scientists have recently shown that certain organisms can exist without oxygen for many years at a time. 

These unique organisms have developed various biological adaptations allowing them to conserve energy, shift their metabolism, and survive in environments where light and oxygen are extremely scarce or completely nonexistent. 

Most of these organisms exist within very harsh conditions within the deep oceans or extreme environments of other living creatures. 

READ | Which Bird is Known As the Harbinger of Spring?

What are the animals that can live without oxygen?

Here is the list of animals that can live without oxygen: 

Source: bioexpedition.com

1. Tardigrade (Water Bear)

Tardigrades are microscopic animals often called “water bears.” They are famous for their ability to survive extreme conditions. When oxygen is not available, tardigrades enter a special state known as cryptobiosis. In this state, their metabolic activities almost completely stop. 

This allows them to survive without oxygen for long periods, along with other harsh conditions such as extreme temperatures, radiation, and dehydration. Once normal conditions return, they become active again.

2. Epaulette Shark

The epaulette shark inhabits the shallow waters of the Great Barrier Reef in Australia; it can survive for several hours in an extremely low-oxygen environment. Epaulette sharks are often left stranded in pools of low oxygen during low tides; however, they can slow their metabolism and lower their oxygen consumption when there is not enough oxygen in the water.

The epaulette shark, though it cannot survive without any oxygen at all, is one of the most tolerant vertebrates to low oxygen levels.

3. Icefish

Icefish live in the freezing waters of the Southern Ocean near Antarctica. They are unique because they do not have hemoglobin, the protein that carries oxygen in blood. Instead, oxygen dissolves directly in their blood plasma due to the cold, oxygen-rich environment. While they do not live entirely without oxygen, their survival with such an unusual system highlights a rare adaptation to extreme conditions.

4. Hydra

Hydra are jellyfish-like, freshwater invertebrates. Their body are thin and allow oxygen to diffuse through them easily into their cells; therefore, they do not need any complex respiratory organs or systems to tolerate being immersed in water that has very low oxygen levels for an extended period.

5. Spiny-Headed Worm (Loricifera)

Loriciferans are microscopic marine animals discovered in deep-sea environments where oxygen is completely absent. These animals use alternative biochemical processes that do not rely on oxygen. 

Instead of mitochondria, they have specialized structures that allow them to produce energy in oxygen-free conditions, making them one of the few known animals that permanently live without oxygen.

Recommended Reading:

List of the U.S. States With Most Alligators