The naked mole-rat comes from East Africa, so they live completely undeground.
They are highly adapted to living undergound.
Most of the borrow is composed of
foraging tunnels, which if you add them up can
extend for 3 or 4 km, so massive, massive labyrinths
but because those tunnels are dug
searching for roots and tubers,
their food resources
they tend to be at the level of the roots so within half a meter
or a meter of the
surface. The more central core areas of the burrow
where you find communal nesting chambers and
communal toilet chambers, they
can be deeper.
Once in Kenya we dug down to a nest chamber, it was about 5 feet
underground, which is
quite a lot of digging
clearly, that's difficult for predators to get at
even the snakes that can get into burrows
and I think
also is very thermo-stable
down at that level as well
which is good for these cold blooded
mammals.
The original
founder stock
came form Kenya.
They were collected by someone who did a PHD
in the wild, on their ecology and behavior and they brought
some animals back to London.
Their lifestyle was really the first thing that intrigued
biologists going back to the late seventies, early eighties when it was realized that
the naked mole rat actually
behaved like a social insect.
We have animals living together in very large groups
on average, you know
eighty to a hundred in the wild, sometimes up to three hundred though
yet within these enormous colonies
there is just a single breeding female,
the Queen, she mates with one or two maybe three reproductive males that
she selects and then the rest of the colony of both sexes
are reproductively suppressed,
they help basically.
Some of the bigger ones may
become non workers and adopt a defensive role
so in the non-breeders if you
take a male and a female out the surpressing influence of the colony and
pair them togther away from the suppressing infefluences of the queen
they will quite rapidly
become reproductively active.
The work has
broad implications in understanding
captive breeding and
reproductive suppression in other species and even may be in humans. The
mechanisms are probably
likely to be very similar.
So the queen generally has an elongated body.
After having a few, the first few litters the vertebrae
get longer
to help
accommodate these large litters, she is also
the one that normally
tramples over the top of everyone else when they meet in
the tunnels
on face to face encounters.
She's probably in the first
twenty or thirty days of pregnancy
maybe halfway through the seventy two days, so the pregnancy is actually quite
long for a rodent as well.
Towards the end
when the queen is very very
large and pregnant
because they can have
twenty-seven offspring in one litter, she would have a great difficulty in
getting down, especially the smaller tunnels in the wild
and would be dependent on the work-force bringing
food back.
You can see that although they are called naked mole rats,
they are not in fact completely naked because they have
sensory whiskers scattered along the body
which gives them an important tactile sense, given that they are
living in
total darkness. If we get this one to turn round
head on that you can see the
teeth that protrude
outside the mouth, those front incisors which is what they use to dig
the burrows
and the
mouth seals behind them so that they don't swallow soil as they are digging away.
The external ear is also absent.
Their gut contains quite a
potent mixture of microorganisms which helps them to
ferment the high cellulose content of the food
also gives rise to
one of the more unpleasant aspects of mole-rat behaviour which is Coprophagia
so when the young are being weaned
they eat the faeces of the adults in order to infect their
digestive tract with these all important microorganisms.
Some of the animals we can see here
will be over 20 years old
and going strong. The last time I asked a colleague in the States, she had some
at
about 32 years
so we probably don't know the upper limit just yet.
Another thing
was that they appear
not to get any of the usual age related problems including Cancer.
Recently, there has been 2 separate naked mole-rat genome projects and
so far
the genome project has
revealed that some of the
genes that we would expect; cancer, genes related to low oxygen,
genes that are implicated in aging, have been shown to be doing different things in
naked mole rats. It will have wide ranging for implications for human and
and animal health, and understanding Biology in general.