Isegoria

Researchers find yet another reason why naked mole-rats are weird:

For example, instead of generating their own heat, they regulate body temperature by moving to warmer or cooler tunnels, which lowers the amount of energy they need to survive. They’re also known to have what Park calls “sticky hemoglobin,” which allows them to draw oxygen out of very thin air. And because they live underground in large social groups, they’re used to breathing air that’s low in oxygen and high in carbon dioxide.

[...]

To start out, he and his colleagues tested how well the mole-rats fared in a chamber with only 5 percent oxygen, which is about a quarter of the oxygen in the air we breathe, and can kill a mouse in less than 15 minutes.

They watched closely, ready to pull the mole-rats out at the first sign of trouble.

“So we put them in the chamber and after five minutes, nothing. No problems,” Park says. An hour later, there were still no problems.

Five hours later, the researchers were tired and hungry and ready to go home, but the mole-rats could’ve kept chugging along.

“Oh, I think so,” says Park. “They had more stamina than the researchers.”

The animals had slowed down a bit, he says, but were awake, walking around and even socializing.

“They looked completely fine,” he says.

Next, the researchers decided to see how the mole-rats dealt with zero percent oxygen.

“And that was a surprise, too,” he says.

Such conditions can kill a mouse in 45 seconds.

The four mole-rats involved in this leg of the study passed out after about 30 seconds, but their hearts kept beating and — a full 18 minutes later — the mole-rats woke up and resumed life as usual when they were re-exposed to normal air. (The three mole-rats that were exposed for 30 minutes, however, died.)

[...]

When the researchers looked at tissue samples taken from the mole-rats at various times during the oxygen deprivation, they noticed a spike in levels of another sugar, fructose, about 10 minutes in.

“We weren’t looking for it, but bang, fructose goes way up in the blood and then it goes way up in the organs and it gets used by heart and brain,” Park says.

The naked mole-rats appear to have the option of switching fuels from glucose, which requires oxygen to create energy, to fructose, which doesn’t.

Humans are capable of storing and using fructose in the liver and kidney, but as Park explains, we don’t have enough of the correct enzyme to create energy directly from fructose. Nor do we have enough of the proteins necessary to move fructose molecules into the cells of vital organs. Our cells have to convert it into glucose in order to use it.

The cells in the brain, heart, liver and lungs of naked mole-rats are all outfitted with proteins that moves fructose into the cells, and with the right enzyme to create energy from it.

“They have a social structure like insects, they’re cold-blooded like reptiles, and now we found that they use fructose like a plant,” Park says.

“No sci-fi alien is so startlingly strange” as an octopus, Sy Montgomery noted, but they’re even stranger than we realized:

Rosenthal and Eisenberg found that RNA editing is especially rife in the neurons of cephalopods. They use it to re-code genes that are important for their nervous systems — the genes that, as Rosenthal says, “make a nerve cell a nerve cell.” And only the intelligent coleoid cephalopods — octopuses, squid, and cuttlefish — do so. The relatively dumber nautiluses do not. “Humans don’t have this. Monkeys don’t. Nothing has this except the coleoids,” says Rosenthal.

It’s impossible to say if their prolific use of RNA editing is responsible for their alien intellect, but “that would definitely be my guess,” says Noa Liscovitch-Brauer, a member of Rosenthal’s team who spearheaded the new study. “It makes for a very compelling hypothesis in my eyes.”

[...]

Only about 3 percent of human genes are ever edited in this way, and the changes are usually restricted to the parts of RNA that are cut out and discarded. To the extent that it happens, it doesn’t seem to be adaptive.

In cephalopods, it’s a different story. Back in 2015, Rosenthal and Eisenberg discovered that RNA editing has gone wild in the longfin inshore squid — a foot-long animal that’s commonly used in neuroscience research. While a typical mammal edits its RNA at just a few hundred sites, the squid was making some 57,000 such edits. These changes weren’t happening in discarded sections of RNA, but in the ones that actually go towards building proteins — the so-called coding regions. They were ten times more common in the squid’s neurons than in its other tissues, and they disproportionately affected proteins involved in its nervous system.

Having been surprised by one cephalopod, the team decided to study others. Liscovitch-Brauer focused on the common cuttlefish, common octopus, and two-spot octopus. All of these showed signs of extensive RNA editing with between 80,000 to 130,000 editing sites each. By contrast, the nautilus — a ancient cephalopod known for its hard, spiral shell — only had 1,000 such sites.

This distinction is crucial. The nautiluses belong to the earliest lineage of cephalopods, which diverged from the others between 350 and 480 million years ago. They’ve stayed much the same ever since. They have simple brains and unremarkable behavior, and they leave their RNA largely unedited. Meanwhile, the other cephalopods — the coleoids — came to use RNA editing extensively, and while evolving complex brains and extraordinary behavior. Coincidence?

Liscovitch-Brauer also found that around 1,000 of the edited locations were shared between the coleoid species — far more than the 25 or so sites that are shared between humans and other mammals. These sites have been preserved over hundreds of millions of years of evolution.