A colony of 60 million fish with transparent blood has been discovered in Antarctica

The remarkable discovery shows just how little is known about the depths of the oceans.

The vast colony, believed to be the largest in the world, is home to the magnificent ice fish (Neopagetopsis ionah), which has a translucent skull and translucent blood. They are the only vertebrates that do not have red blood cells.

To survive these low temperatures, he developed an antifreeze protein in his transparent blood that prevents ice crystals from growing.

The breeding colony was discovered in February 2021 by the German polar research vessel Polarstern, which was surveying the sea floor about half a kilometer below the ship. It used a car-sized camera system attached to the stern of the ship that transmitted images to the deck as it was towed.

The expedition focused on ocean currents and the discovery of the nests, distinct from the muddy sea floor with a circle of stones, was a surprise.

“We just saw a fish nest after a fish nest for a full four hours, and during that time we covered maybe six kilometers (3.7 miles) from the sea floor,” said Otton Purser, a postdoctoral researcher at The Alfred Wegener Institute in Bremerhaven, Germany. He’s the lead author of a study on the colony of ice fish published in the journal Current Biology on Thursday.

“I’ve never seen anything like this in my 15 years as an oceanographer,” Purser said. “After that dive, we emailed the experts on the beach who knew something about such fish. They said, ‘Yes, that’s very unique.'”

Dramatic range

Four more camera dives revealed the breeding colony’s dramatic extent – and its stunning uniform nature.

“This is really a surprising discovery,” said John Postlethwaite, a University of Oregon biology professor who studies fish. He did not participate in the research.

“It is also important. The extent of the biomass is unexpected to me at least. The extent to which the fish alter the bottom structure of the sediment creates (a) a habitat for a community that ripples the food web to support a large variety of species.”

The researchers said the colony covers more than 240 square kilometers (93 square miles). With an average of one nest per three square metres, they estimated that the colony contained about 60 million active nests.

Each of the evenly spaced nests was about 15 cm (6 in) deep and 75 cm in diameter, containing an average of 1,735 eggs. Most of them were guarded by a single adult fish. Some nests only contained eggs, others were unused.

“The spacing between the nests is a bit like the spacing of birds on a phone line,” Postlethwaite added by email.

“Some animals like to be social, but there is a limit. Gathering may give them advantages for finding mates but it provides a rich source of predation.”

The fish appear to be drawn to an area of ​​warm water, which is about 2 degrees Celsius warmer than the surrounding sea floor, and 0 degrees Celsius cold, Purser said. (Sea water freezes at a temperature lower than that of fresh water.)

The researchers have deployed two camera systems to monitor the ice fish’s nests until the research vessel returns. We hope the photos capture more details about the fish’s nest ecosystem.

One question The researchers want to answer for how long the adult fish guard the eggs – experts believe could be months – and whether the watch is male or female.

“The reproductive behavior of most, if not all, ice fish appears to revolve around male courtship of females by building a ‘good’ nest,” said ice fish expert H. William Detrich, emeritus professor of biochemistry and marine biology at Northeastern University via mail. Email: He did not participate in the search.

The findings revealed a globally unique ecosystem, according to the researchers, and they say it should be designated as a protected area.

Dietrich added: “The implications for the conservation of this species are clear – a marine protected area should be established in the Weddell Sea to prevent the exploitation of this ice fish species.”

The discovery was made by a team aboard the German polar research vessel Die Polarstern vor A74.

Seal food?

While the Weddell Sea is covered in sea ice year-round, the ice is relatively thin—three feet thick—meaning that photosynthesis can still occur and life can occur. growth. The bottom of the Weddell Sea is far from barren, Purser said, with sea sponges, corals, octopuses and star fish lurking along the sea floor.

He said about 2,000 seals also live in the area and are likely to dive into the breeding area and feed on ice fish, although there is no conclusive evidence for it.

While there are species of freshwater fish that make similar types of nests, scientists have “never seen such colonies in the deep sea,” Purser said.

“I think we’ve photographed maybe only 1% of the Weddell sea floor, and who knows what’s hidden around the place. I’m convinced there are many gaps in our knowledge of the deep sea.”

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