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  • 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.

The naked mole-rat comes from East Africa, so they live completely undeground.

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B1 中級 美國腔

裸鼴鼠為什麼能活這麼久? (Why do naked mole rats live so long?)

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    羅紹桀 發佈於 2021 年 01 月 14 日
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