Antarctic Adaptations

Antarctica is a continent of great extremes.

Inside the Antarctic Circle summer brings 24 hours of sunlight, and winter brings 24 hours of darkness.

The average temperature at the South Pole is -18°F (-30°C) in the summer, and -76°F (-60°C) in the winter.

On the coast, winds have measured more than 170 knots (195 mph / 310 kph).

Antarctic species have adapted to Antarctica’s seasonal extremes and cold, windy conditions with many unique adaptations.

aurora australis — Aurora Australis (Southern Lights)

emperor penguins huddled winter — Emperor penguins huddling

Every winter at the South Pole the sun drops below the horizon and most of the continent falls into six months of darkness. The ocean around Antarctica freezes over, surrounding Antarctica in a vast skirt of sea ice, almost doubling the size of Antarctica.

Beneath the ice, fish and other invertebrates thrive in the extremely cold, salty water. Communities of microscopic plants (phytoplankton) live amongst the ice, waiting for the sun to return. Above the ice, male emperor penguins spend up to four months fasting and incubating a single egg balanced on their feet. They huddle in groups to fend off the cold, and keep their egg warm under a slip of skin called a brood pouch.

crabeater seals — Crabeater seals on ice

Humpbacks feeding — Humpback whales feeding

At the end of winter (in mid-September at the South Pole, and around mid-October on the coast) the sun returns and life springs to action. The warmth and light of the sun sparks a cascade of life-giving activity that signals the start of the busy austral summer.

In the Southern Ocean, microscopic sea plants called phytoplankton form the foundation of a vibrant food web. Like plants on land, they use sunlight and carbon dioxide to create energy, and when summer hits the cold, nutrient-rich ocean they grow into blooms so large they can be seen from space.

Phytoplankton feed small crustaceans like copepods and Antarctic krill. Small, shrimp-like crustaceans, Antarctic krill are a keystone species and a fundamental player in the polar food chain. Antarctic krill are the staple diet for most whales, seals and penguins in Antarctica.

Across coastal Antarctica, the summer months are abuzz with biological activity. Seals give birth on the ice and rocky beaches hum busily with penguins nest-building, breeding, incubating and rearing their chicks in the short, sweet summer.

ANTARCTIC EXTREMES

Adaptations

To withstand the extreme seasons and cold, dry climate, Antarctic animals have come up with survival strategies that make them some of the most unique, rare and highly specialized creatures on the planet.

The crocodile icefish (white-blooded fish)

Some icefish, for example crocodile icefish (Chaenocephalus aceratus), have a unique way of absorbing the oxygen they need to survive.

In the frigid waters of the south, an unusual group of fish species have adjusted to the extreme cold. They have developed antifreeze proteins in their blood, and other strange and wonderful adaptations. These fish, collectively called notothenioidei, make up roughly 90% of all the fish in Antarctic continental waters.

The crocodile icefish (white-blooded fish) is a member of the notothenioid family.

Crocodile icefish have no red blood cells – in fact, their blood is pale and translucent! They are the only known adult vertebrates with no red blood cells in their blood.

Red blood cells are important as they help animals transport oxygen from their lungs or gills to the rest of the body, via a protein called hemoglobin. In place of hemoglobin, crocodile icefish have a range of adaptations to help them absorb oxygen including larger gills and smooth, scale-free skin, which allows them to absorb oxygen directly from the ocean.

While their white blood doesn’t necessarily have any evolutionary value for icefish, it may make them particularly vulnerable to rising ocean temperatures. Cold water holds more dissolved oxygen than warmer water. As the ocean heats up and dissolved oxygen becomes less available, their method of absorbing oxygen may become less efficient.

Image credit: Regan, C. Tate

Polar gigantism

Roaming across the floor of the Southern Ocean is a plethora of unusually large invertebrates.

In Antarctic waters, marine creatures such as sea spiders, sponges, worms and some crustaceans grow and grow until they dwarf their distant relatives in warmer waters to the north.

The exact cause of polar gigantism remains an open question. The most widely accepted explanation is the oxygen-temperature hypothesis. According to the oxygen-temperature hypothesis, polar gigantism is a result of the high availability of oxygen in cold, polar waters.

Image credit: Steve Childs

A way of life

Not all Antarctic species have such unusual adaptations. But every animal living in Antarctica has evolved in particular ways that allow them to thrive in this unique polar environment.

Their ability to endure in such extreme environments is expanding our understanding of life, its limitations and its incredible capacity to thrive in even the most forbidding environments.