Cryptic remains of tiny animals have been found in an Antarctic lake

To their surprise, scientists from Antarctica discovered what appeared to be tiny animal remains in mud dredged in a lake covered with a thick coat of ice for thousands of years.

The researchers on this expedition, known as SALSA, are the first to sample Lake Mercer, a waterbody about 600 kilometers from the South Pole. After drilling about a kilometer through the ice at the end of December, researchers lowered the instruments that brought water and sediment to the surface.

By examining these specimens under the microscope, the team discovered "objects that looked like crushed spiders and crustacean-type objects with legs … others that could look like worms," ​​says David Harwood, expedition member, micropaleontologist at the university. of Nebraska – Lincoln. The researchers also spotted what appeared to be the vestige of a very resistant microscopic creature called a water bear (SN online: 14/07/17). The DNA examination of these remains will help researchers to identify them more precisely.

This discovery, reported for the first time online by Nature On January 18, "it really intrigues," says Slawek Tulaczyk, a glaciologist at the University of California at Santa Cruz, who is not part of the SALSA team. Until now, scientists have not considered these Antarctic lakes like Mercer as environments conducive to the proliferation of organisms larger than microbes.

In 2013, researchers sampled Whillans Lake, the only other ice – covered lake in Antarctica in which scientists plunged: "We have found no evidence of a more complex element than". a microbe, "says Brent Christner, a member of the SALSA team, a microbiologist at the University of Florida at Gainesville (SN: 20/09/14, p. ten). "We had a similar expectation here."

Tale of two lakes

The remains of animals recently discovered at Mercer Lake particularly surprised the researchers because samples taken from a nearby lake, Whillans Lake, contained only microbes.

It is still unclear whether the newly discovered animal carcbades were left behind by creatures that actually lived in Mercer Lake, explains Tulaczyk. Ice or water may have carried these fragments from the ocean or lakes further upstream in the Trans-Antarctic Mountains. The carbon dating of the samples could help determine their age, which could provide a clue to the timing and date of arrival of these tiny animal carcbades in Mercer Lake, he said. .

If one of these animals inhabited Lake Mercer, it is possible that some of them are still fighting, says Harwood. "It's interesting to think that life can exist in extremely extreme environments," like an Antarctic lake cut off from the ocean and the atmosphere for thousands of years, says Harwood. "If life still persists, it's important for our thoughts on what we might discover in space."