Researchers were startled to find fish, crustaceans and jellyfish in cold and dark water nearly 2,500 feet (740 meters) below the Antarctic ice.

The research team was drilling on the Ross Ice Shelf, a glacier the size of France off the coast of Antarctica, to investigate stability of the Whillans Ice Stream, a major glacier flowing into the shelf. They employed Deep-SCINI, a remotely operated vehicle designed to travel through narrow fissures in the ice.

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The fish they saw was the length of a butter knife or are about 8 inches (20 centimeters) long. It has bulb-eyes and its internal organs show through its translucent, pinkish body. Deep-SCINI encountered between 20 and 30 animals throughout the day, including black and orange fish, dozens of crustaceans and other marine invertebrates.

There were also amphipods, a type of crustacean that thrives in the ocean's harshest environments. The species are in one of the world's most extreme ecosystems and hidden beneath the Ross Ice Shelf.

Life at the grounding line is limited to only 33 feet (10 meters) of freedom between the ice and seafloor in seawater about 28 degrees Fahrenheit (minus 2 degrees Celsius).

How the fish survive in such extreme and closed environment is unclear.

"We have to ask what they're eating. Food is in short supply and any energy gained is hard-won. This is a tough place to live," Brent Christner, a microbiologist from Louisiana State University, told Scientific American.

Experts believe that in the absence of sunlight, life could be powered by chemical energy, like ammonium from the Earth's interior.

Christner believes the water and mud samples they collected will help answer the many questions that remain.

TagsAntarctic region, Antarctic, marine animals, crustaceans, jellyfish, Antarctica, sea species