Naked mole rat

## Physical description 
Typically, the animals are between eight and ten centimetres long, and weigh about 30&nbsp;grams. Their eyes are quite small, and they do not see very well. Their legs are thin and short. Nevertheless, they are very good at moving underground and can move backward as fast as they can move forward. They have large, protruding teeth, which they use to dig. Their lips are sealed just behind the teeth to prevent soil from filling their mouths while digging. They have little hair and wrinkled pink or yellowish skin.

The naked mole rat is well adapted for the limited availability of oxygen within the tunnels that are its habitat: its lungs are very small and its blood has a very strong affinity for oxygen, increasing the efficiency of oxygen uptake.  It has a very low respiration and metabolic rate for an animal of its size, about two thirds that of a mouse of the same size. It only uses very little oxygen.  In long periods of hunger, such as a drought, its metabolic rate can reduce by up to twenty-five percent.

The naked mole rat can only regulate its body temperature in the typical mammalian fashion over a relatively narrow range of temperatures. Outside this range, it overheats or cools. It can overcome this by its behaviour. When cold, naked mole rats huddle together or bask in the shallow parts of their burrow systems. When they get too hot, they retreat to the deeper, cooler parts of their tunnel system.

## Ecology and behavior 
### Distribution and habitat 
The naked mole rat is native to the drier parts of the tropical grasslands of East Africa, mainly South Ethiopia, Kenya, and Somalia.

Colonies averaging 75-80 individuals live together in complex systems of burrows in arid African deserts. The tunnel systems built by naked mole rats can stretch up to two or three miles in cumulative length.

### Social structure and reproduction 
The naked mole rat is one of the two species of mammals that are eusocial. Only one female (the queen) and one to three males reproduce, while the rest of the members of the colony are workers. Workers do different things. In the wild, naked mole-rats usually breed once a year, if the litter survives. In captivity, they breed all year long and can produce a litter every 80 days. The secret of their longevity is debated, but is thought to be related to the fact that they can shut down their metabolism during hard times, and so prevent oxidative damage. This has been summed up as "They're living their life in pulses".

Due to their extraordinary longevity for such a small rodent, an international effort was put into place to sequence the genome of the naked mole rat.  Results came in 2011 and 2014. Transcriptome sequencing showed that genes related to mitochondria and oxidation reduction processes have high expression levels in the naked mole-rat as compared to mice. This may contribute to their longevity.

The DNA repair transcriptomes of the liver of humans, naked mole rats and mice were compared.  The maximum lifespans of humans, naked mole rats, and mice are respectively ~120, 30 and 3 years.  The longer-lived species, humans and naked mole rats, expressed DNA repair genes at a higher level than did mice.  In addition, several DNA repair pathways in humans and naked mole rats were up-regulated compared with mice.  These findings suggest that increased DNA repair makes for greater longevity. The findings are consistent with the DNA damage theory of aging.

## Conservation status 
Naked mole rats are not threatened. Despite their tough living conditions, naked mole rats are quite widespread and numerous in the drier regions of East Africa.

## References 
## Other websites 
*Page on the Animal Diversity Web
*More photos 
**Heterocephalus glaber* images at bioimages.vanderbilt.edu 
*Naked mole-rat webcam