At a meeting of experimental biologists this week in Campos do Jordão, Brazil, Rochelle Buffenstein from Calico labs in San Francisco gave a plenary lecture on the naked mole-rat, whose amazing longevity is just one of its fascinating traits.
This east African rodent has a life span of more than 30 years, which is 10 times longer than that of a mouse, and extraordinary for such a small mammal. According to Buffenstein, this longevity is partly due to telomeres—the end sections of chromosomes that, at least in humans, get shorter with each cell division. For some still unknown reason, this is not the case with naked mole-rats. Human fetal cells can only divide 52 times, but naked mole-rat cells can divide 115 times (and counting!). Even more amazing, they can breed until they die, and their risk of dying actually decreases with age. They don’t seem to undergo senescence, or all the problems associated with getting old.
Also legendary is the naked mole-rat’s ability to resist cancer. This is not yet understood either, but may have something to do with an extra gene that fights cancer, and some kind of tumor suppressor process.
The naked mole-rat is certainly not the most beautiful species, at least not in the eyes of human beholders. But some of its characteristics make it extremely interesting for astrobiology. Naked mole-rats are in fact multicellular extremophiles. They live in burrows that can be several kilometers long, under constant oxygen deprivation. Oxygen levels are usually at about two to nine percent in these burrows, rather than the 21 percent we humans enjoy at the surface. And Buffenstein reported that Thomas Park and others have shown that these hardy creatures can survive zero percent oxygen for at least 18 minutes, with no apparent ill effect. They have a respiration rate much lower than that of a mouse, and they can drop their metabolic rate even further if needed.
Naked mole-rats live in colonies of 20 to 300 individuals, with a social structure called eusociality, similar to what we see in ants, termites, and bees. There is only one queen that reproduces with less than a handful of males (sometimes only one), while the rest of the colony functions as workers. The naked mole-rat also is the only mammal that is for the most part cold-blooded, with no ability to regulate its temperature except in a very narrow range. It feeds on certain enlarged structures that some plant species use to store nutrients. Interestingly, they do not destroy these structures, but allow the plant to regenerate so they can continue feeding on them.
Based on all these odd behaviors and abilities, naked mole-rats are a great example of how different extraterrestrial life might be. Could there be a mammal on another world that lives in an insect-type colony, farms plants, and evolves to form a technologically advanced society? I think it’s entirely possible!
Want to see these “alien” animals for yourself? Watch the new naked mole-rat live cam at the National Zoo.