Why Don't Fish Freeze In Antarctica?

When we mentioned Antarctica, most of you would be thinking about how cold this place is for humans to survive in. The temperature here is way below freezing point with the cold breeze and no existence of such vegetation.

Despite all of that, there are still a few people living in such harsh environments. More importantly, how does any creature like fish manage to survive the icy cold water? What kind of adaptations do they have to be able to sustain all year long?

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Cold-Blooded Animals

We commonly hear the term cold-blooded animals which also includes fish but do we know what that actually means?

A cold-blooded organism is an animal whose body temperature is dependent on its surroundings. This comprised almost all fish, reptiles, and amphibians.

In contrast for warm-blooded, they maintain their own body temperature. Most warm-blooded animals will find it hard to adapt to a range of temperatures. This commonly can be found in mammals and birds.

Opah which is a fish species found in Hawaii is a warm-blooded animal. But then this does not happen to fish in the Antarctic Ocean as the fish found here are composed of cold-blooded creatures but have revolutionized with interesting adaptations.

The Danger of Freezing Temperature

To survive and keep on living, blood must flow to all parts of the body. This is because blood carries oxygen and essential nutrients for the body's growth and repair. So what happens if warm-blooded creatures like humans were to live in Antarctica?

One has to take note that a big portion of our blood consists of water or 90% of them to be exact. This means that our blood will totally freeze in the Antarctic waters.

And because of the salt content in the ocean, the freezing temperature of the water is -1.9°C(28°F). The freezing point below zero causes the formation of crystal ice in our blood. As crystals are formed, they will destroy all the cells available in our body.

Since the cold-blooded fish cannot rely on its own body temperature to live, it must find a way to overcome the freezing temperature.

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Anti-Freeze Blood

Anti-freeze refers to a particular substance that can be added to the water to reduce the freezing point. The way anti-freeze works are that it blocks the formation of ice crystals.

For Artic fish, the substance required is an anti-freeze protein created by the fish. It is made similarly to other proteins in the body and this was discovered by Dr. Arthur L. DeVries, a professor from Illinois University in the 1960s.

It was discovered when the world was wondering how fish managed to survive in the cold temperature. But the question remains, what did the protein do to prevent the blood from freezing?

Ice is formed when the dense water becomes a particular lattice crystal.

In simpler terms, the water will condense when the molecules become close to one another. And when the space between the molecules become lesser, the water molecule will attract one another with a stronger bond to create a lattice crystal.

What is being done by the anti-freeze protein in the fish blood is that it is incorporated into this lattice crystal and prevents it from fusing. If these crystals cannot fuse with one another they will not form ice in the blood.

Or at least it will not be able to form an ice crystal big enough to cause harm to the fish. What's interesting is that this does not only occur in fish alone.

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Anti-Freeze in The Nature

The Antarctic fish is not the only living creature with this adaptation. This anti-freeze protein can also be found in various organisms. This adaptation can be seen in most primitive organisms such as diatoms in sea ice and certain bacteria.

In fact, it can also be present in revolutionary organisms like snow mold and several species of beetles. This adaptation has expanded in different ways but will ultimately achieve the same goal.

In evolutionary research, this phenomenon is known as convergent evolution. Basically, it is quite similar to other different pathways on the map that will eventually reach the same destination.

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