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Naked Mole Rat Queen with Offspring

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 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).

06_12_Digging_side

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).

naked-mole-rats

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?

Family Portrait?

(Picture: AFP/Getty Images)

(Picture: AFP/Getty Images)

Every day, major news outlets pick up a few trivial “offbeat” stories in order to pad out the international mayhem, barely concealed commercials, punditry, and celebrity gossip which constitutes the news. One such puff-piece in the news today features the story of a spa in Tokyo which is offering snail facials.  Apparently credulous yet affluent Japanese women can pay to have snails crawl on their face for approximately an hour. The snails are fed on organic carrots and greens so that their mucous–and whatever else passes out of them–will be, well, organic.

There is a rationale behind this wacky beauty regime.  Snail slime contains hyaluronans (aka hyaluronic acids), long unbranched polysaccharides found in animal tissues which promote healing and flexibility.  Hyaluronans have been found to play a major role in wound healing and it is a major component of cartilage and skin (they are also implicated in the prevention of cancer—and malfunction of hyaluronan-producing cells is likewise implicated in cancerous mutagenesis).  Cash-seeking dermatologists have long used hyaluronan as a “filler” to inject into skin to minimize the appearance of wrinkles and as a relatively inert ingredient in their creams and unguents, however recently hyaluronans made the news in an even bigger way with a fascinating, albeit erudite article about the longevity of naked mole rats.  You can read the actual research abstract here, but ABC News more concisely summarizes the possible implications of the research by writing, “Last month, researchers at the University of Rochester wrote that naked mole rats’ super-long hyaluronan molecule actually tells cells to stop reproducing, which is why they think naked mole rats don’t get cancer.”

Heterocephalus glaber: The naked mole-rat

Heterocephalus glaber: The naked mole-rat

Unfortunately, whatever actual importance hyaluronans have in the human body (and whatever importance super long hyaluronans have for the doughty naked mole rat), it does not seem that being coated in snail mucous necessarily has much benefit.  Dermatologists aver that, as the snail slime (which may be of dubious benefit anyway) simply lies on top of the dead waterproof dermis, it cannot have much if any magic mole-rat age-reducing effect.  That still doesn’t deter desperate people who let gastropods crawl all over their face in a quest for eternal youth.

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