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Letter from Stephanie: Antarctic Adaptations

Part of Hall of Ocean Life.

Dear Fellow Explorers,

We are working close to the edge of the sea ice–and the wildlife is amazing! We've seen orcas, Emperor penguins, crabeater seals (they don't eat crabs), and leopard seals (they eat anything they want). We've also seen several species of birds. I'm not a bird expert, but my friend Nancy identified them as storm petrels and Antarctic terns.

As you know, working in Antarctica means dealing with some of the most extreme conditions on Earth. Our bodies are not naturally adapted to the environment here; so we need to carry our "adaptations" with us. We bring along our food, shelter, water, and warm clothing to help us survive in the harsh environment, and we have all kinds of high-tech gear to help us cope with the extremely cold, windy, dry conditions.

The plants and animals of Antarctica, however, don't have any high tech gear. They don't need it! All of them have developed interesting adaptations to survive the harsh environment, from physical to behavioral to chemical adaptations. And many of these animals' adaptations work together in incredible ways.

Physical adaptations are sometimes the easiest to spot. Many of the animals living in Antarctica have outer layers of dense fur or water-repellent feathers. Under this fur or feather layer is a thick layer of insulating fat. Many marine animals have large eyes to help them spot prey and predators in the dark waters. They are further protected by their coloration, dark backs, and light undersides. This way, they are hard to spot from above, because they blend into the dark sea floor; from below, creatures looking up see the bright light from above, and so it is hard to spot a pale belly! This adaptation helps predators stay hidden from prey and prey stay hidden from predators.

Some physical and chemical adaptations are less obvious. Orcas and penguins, for example, have circulatory systems adapted to conserve heat. Their veins wrap around their arteries, warming the blood in the arteries and saving energy. Plants and lichens that live on ice-free areas of the continent have special leaf structures that prevent loss of moisture; in the Antarctic desert, every bit of moisture counts! And because plants have to make their own food, many Antarctic plants increase the rate of photosynthesis to make food faster and at lower temperatures.

 Behavioral adaptations are another way that organisms adapt to the extreme environment of Antarctica. Some birds and whales migrate to Antarctica each summer, leaving for warmer climates during the harsh Antarctic winter. The Arctic tern is probably the most incredible example; if you are wondering why the Arctic tern is named for an area in the North Pole, you're right! The Arctic tern flies 35,000 km (21,750 miles) every year in order to catch the Arctic summer for one half of the year and the Antarctic summer for the other half!

Would you like to take a swim in water at a temperature of -2ºC ? (To compare, consider that the average swimming pool is kept at about 25ºC.) How do fish survive in such cold Antarctic waters? Antifreeze, of course! Certain fish have antifreeze proteins that lower the freezing point of their blood. These proteins attach to the small ice crystals that enter the circulatory system through the gills and prevent the ice crystals from growing. These proteins can also work on crystals that are ingested by the fish as they swim. This is a great example of chemical adaptation.<