Naked Mole Rats

Naked Mole Rat Queen with Offspring

Naked Mole Rats (Heterocephalus glaber) are unique among mammals in that they are eusocial (well actually Damaraland mole rats might be eusocial too, but they are in the same family, the Bathyergidae).  Like bees or ants, mole rats live in a hive society: only one naked mole rat female is fertile and she gives birth to sterile workers who maintain and protect the underground burrows where the colony lives.  A queen breeds with 3 or 4 male naked mole rats and she jealously guards her reproductive monopoly.  If other female naked mole rats begin to produce sexual hormones or behave in a queenlike manner, the queen will viciously attack them.  When the old queen dies, violent battles can break out to become the new queen.  Once a victor emerges, the spaces between her vertebrae expand and she becomes longer and larger. Mole rats breed all year and they can produce a litter of three to twelve pups every 80 days.

Naked Mole Rat (Heterocephalus glaber)

Naked mole rats live in the arid parts of Kenya, Somalia, and Ethiopia.  They feed on huge tubers which weigh as much as all the mole rats in a colony.  The mole rats eat the tubers slowly from the inside, which give the roots time to regrow.  Additionally mole rats can efficiently recycle food, so newly weaned mole rats are fed feces (which can also provide sustenance for adults).    Naked mole rats have huge sharp incisors for tunneling.   Their lips close in such a way that the incisors always remain outside their mouth–so the mole rats can tunnel indefinitely without getting dirt in their mouths.   Worker mole rats are 8 to 10 cm (3 to 4 in) long and weigh 30 to 35 grams (1.1 to 1.2 oz), although the queen grows much larger.  Naked mole rats have weak eyes and tiny skinny legs.  In effect they are pale pink wrinkled tubes with a few long sensitive whisker-like hairs sprouting from their bodies.  They move equally quickly forwards and backwards through their elaborate tunnels (which can measure up to 5 kilometers (3 miles) in total length).

Mole rats are unusual among mammals in other significant ways as well.  Naked mole rats do not maintain same thermal homeostasis as other mammals.  Their body temperatures are much closer to the ambient temperature in their burrows.  If they become unduly cold, they move to the top tunnels of their burrows and huddle together.  If they become hot, the naked mole rats retreat into the bottom levels where the temperatures are cooler.

Oxygen is a precious commodity in the underground tunnels of mole rats, so the fossorial roents have evolved extremely efficient blood and lungs in order to maximize oxygen uptake.   Additionally mole rats have very low metabolic rates compared to other (non-hibernating) mammals.  Their hearts beat slowly:  they breathe shallowly and eat little. In times of drought or famine, they are capable of going into a survival mode where their already slow metabolisms drop another 25 percent.  Naked Mole rats lack a critical neural transmitter which would allow them to feel certain sorts of pain sensations (such as pain caused by acid or hot pepper).  It is believed that the mole rats lost the ability to feel such sensations because the high carbon dioxide levels in their tunnels lead to extremely acidic conditions (mole rats are also surprisingly acid resistant, although I shudder to think of how we know this).

Mole rats live a long time—some captive mole rats are in their early thirties—and they do not age like other mammals but remain young and fit throughout their lives.  Additionally mole rats are untroubled by cancers.  It seems the underlying cause of this remarkable cancer-free long life is a certain hyaluronan (HMW-HA), a gooey peptide which fills up gaps between cells.  The fact that cells do not grow closely together prevents tumors from ever forming.  Hyaluronans exist in all other mammals (and in other animals).  The complex sugars are part of our joints and cartilage.  However the hyaluronan found in naked mole rats is much larger and more complicated.

Thanks to their ant-like colonial life and bizarre appearances, naked mole rats might seem quite alien, but they are near cousins to humans (primates and rodents are close relatives—which will surprise nobody who has ever known a businessperson).  They even come from the same part of Africa as us. The naked mole rats are social animals and they care deeply for one another over their decades of life.  Additionally our kinship with the wrinkly pink rats could provide other benefits.  Humans suffer greatly from aging and cancers.  Mole rats–with their remarkable hyaluronans–could provide workable insights into how to alleviate cancer and aging.

Family Portrait?