Creature Feature: Naked mole-rat

As humans looking around the animal kingdom, we find that some animal “superpowers” are obvious: Birds can fly! Fish can breathe underwater! Lizards can change colors! But often, an animal’s most incredible feats are those that aren’t visible.

Cue the naked mole-rat.

Naked Mole-rat
Naked mole-rat. Image © Smithsonian’s National Zoo.

The naked mole-rat (Heterocephalus glaber), native to Eastern Africa, is a very atypical mammal with some incredible superpowers. These little critters (3-4 inches in length) are mostly hairless with poor vision, which makes sense considering they spend most of their life underground. Groups of ~80 individual mole-rats work together to create an extensive network of underground rooms and tunnels, sometimes up to 5 km (~3 miles) in length! In order to dig these tunnels, mole-rats use their long teeth, which rest on the outside of their lips so they can dig without swallowing dirt [1].

Mole rat teeth
Naked mole rat teeth are on the outside of their lips. Image © Josh More

While most mammals are considered thermoregulators, naked mole-rats are thermoconformers; their body temperature is highly influenced by the surrounding temperatures, as opposed to being controlled internally. This means that mole-rats show a lot of thermo-regulatory behaviors – when they get cold, they huddle; when they get hot, they burrow deeper into the cool earth [1].

8172940409_3aa50bdb19_o
Naked mole-rats huddle together as a form of behavioral thermoregulation. Image © Theron Trowbridge.

Additionally, while naked mole-rat body temperature regulation is more like that of a reptile than a mammal, their breeding system is more like that of an insect! In fact, naked mole-rats are one of only two mammals that show eusociality (the other is another mole-rat, the Damaraland mole-rat).

Though, this eusocial mammal is probably quite stressed being kept apart from other kin!
The naked mole-rat achieved pop-culture fame in Disney’s Kim Possible!

Naked mole-rat breeding, like that of many insect colonies, is dominated by a single breeding female – the queen – and one to three breeding males. This system, where most of the population forgoes reproduction to a small number of individuals, is called eusociality. When the queen dies, the vacancy is filled by another female in the colony, often after a violent fight. The rest of the individuals in the colony are divided among different castes. These castes (while more continuous than discrete) are defined by both physiological differences as well as a differentiation of labor. Naked mole-rat workers – the smallest individuals – oversee building and maintaining the tunnel system as well as collecting and gathering food (usually tubers, parts of plant stems) at the central nest. The mid-sized caste – the soldiers – are the first to react if the tunnel system is attacked. The largest mole-rats (the “non-workers”) often assist in caring for the queen’s pups and may serve as “temperature buffers” – huddling with these individuals reduces the energy spent on temperature regulation for the colony as a whole [2].

mole rat_cape
Super mole-rat! Image © Tim Evanson.

Now, naked mole-rats are clearly fascinating and strange mammals, but nothing so far has indicated a superpower…but these hairless little creatures also show a tendency towards invincibility.

Naked mole-rats are the world’s longest-living rodent (living ~30 years in captivity, 9 times longer than similarly-sized mice) and, additionally, show very few signs of aging. Aging is defined as a gradual deterioration of the body over time that leads to increased mortality and decreased fertility. However, naked mole-rats maintain the same body condition for approximately 90% of their life, with no apparently declines in fertility or increases in mortality with age [3]! In addition to their long, healthy lives, naked mole-rats lack certain neurotransmitters in their skin, which means they are insensitive to some types of pain [4]. Naked mole-rats are also capable of surviving for long periods with very little oxygen, and nearly 20 minutes with no oxygen [5]! Lastly, these vital critters are well-studied in the medical community, as they are highly resistant to cancer [6]. Now THAT is a superpower!


Ryane Logsdon in a member of the Animal Behavior Graduate Group. Her work aims to understand the influences of social and structural environments on courtship behavior in the Greater sage-grouse.


 

[1] Sherman, P., Jarvis, J., & Braude, S. (1992). Naked Mole Rats. Scientific American, 267(2), 72-79.

[2] Jarvis, J. M. U. (1981). Eusociality in a Mammal: Coopertive Breeding in Naked Mole-Rat Colonies. Science, 212(4494), 571-573.

[3] Buffenstein, R. (2008). Negligible senescence in the longest living rodent, the naked mole-rat: insights from a successfully aging species. Journal of Comparative Physiology B, 178(4), 439-445.

[4] Park, T.J., Lu, Y., Jüttner, R., Smith, E.S., Hu, J., Brand, A., Wetzel, C., Milenkovic, N., Erdmann, B., Heppenstall, P.A., Laurito, C.E., Wilson, S.P., & Lewin, G.R. (2008). Selective inflammatory pain insensitivity in the African naked mole-rat (Heterocephalus glaber). PLoS Biology, 6(1), e13.

[5] Storz, J.F., & McCelelland G.B. (2017). Rewiring metabolism under oxygen deprivation. Science, 356(6335), 248-249.

[6] Buffenstein, R. (2005). The naked mole-rat: a new long-living model for human aging research. Journal of Gerontology: Series A, 60(11), 1369-1377.

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