Colony of 60 million fish with transparent blood discovered in Antarctica

A breeding colony of 60 million fish has been discovered in Antarctica's ice-covered Weddell Sea -- a unique and previously unknown ecosystem that covers an area the size of Malta.

The fascinating find shows how little is known about the ocean depths.

The vast colony, believed to be the world's largest, is home to the remarkable icefish (Neopagetopsis ionah), which has a see-through skull and transparent blood. It's the only vertebrate to have no red blood cells.

To survive at such low temperatures, it has evolved an anti-freeze protein in its transparent blood that stops ice crystals from growing.

The breeding colony was discovered in February 2021 by the German polar research vessel Polarstern, which was surveying the seabed about half a kilometer below the ship. It used a car-sized camera system attached to the stern of the ship that transmits pictures up to the deck as it's being towed.

The expedition was focused on ocean currents and the discovery of the nests, made distinct from the muddy seabed by a circle of stones, was a surprise.

"We just saw fish nest after fish nest for the whole four hours, and during that time we covered maybe six kilometers (3.7 miles) of the sea floor," said Autun Purser, a postdoctoral reseacher at the Alfred Wegener Institute in Bremerhaven, Germany. He's the lead author of a study on the icefish colony that published in the journal Current Biology on Thursday.

"I'd never seen anything like it in 15 years of being an ocean scientist," Purser said. "After that dive, we emailed the experts on shore who know about fish like this. They said, yep, this is pretty unique."



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