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The Amazing Naked Mole-Rat
You’ve heard of the lab rat and the lab mouse, and maybe you’ve even heard of the laboratory fish and frog. But, have you ever heard of the lab naked mole-rat?
This creature, although it may appear quite alarming, has fascinating characteristics that make it an exciting newcomer to a number of fields of research. In particular, the naked mole-rat has an impressive lifespan, living up to 30 years in the wild, approximately ten times longer than mammals of a similar size (laboratory mice live to about 2 years old). On top of that, naked mole-rats are not sensitive to certain painful stimuli, specifically acid and capsaicin (Park et al., 2008) and have never shown signs of cancer thus far.
The naked mole-rat normally inhabits elaborate underground tunnel networks in East Africa. They have an extremely unusual social structure for the mammalian world; like bees and ants, they are eusocial creatures, meaning that they have a queen that is responsible for all reproduction in a colony. Also, all working tasks are divided among social castes.
The mole-rat tunnel environment is very low in oxygen and has high carbon dioxide levels. The mole-rat survives by feeding on tubers that protrude beneath the ground. Matching this lifestyle, they have poorly developed eyesight, and jaw muscles that make up 25% of their total muscle mass.
Laboratories currently studying this unusual animal model are pursuing a variety of avenues, including the mole-rat’s natural resistance to hypoxia-induced tissue damage (Peterson et al., 2012), resistance to cancer, lack of response to noxious stimuli (Park et al., 2008) and social structure. Recently, behavior studies comparing naked mole-rats with C57Bl/6 mice have been carried out in order to better understand the naked mole-rat as an animal model. These studies focused on anxiety, cognition, and motor skills.
Overall, the authors found evidence for a distinct lack of motor skills in the naked mole-rat. Muscle strength was assayed using the inverted screen and static rod tests. The mole-rats appeared to have poor grip reflexes and poor muscle strength. During the elevated plus maze test, the mole-rats showed no preference for the open or closed arm, and even fell from the maze several times. In the Open Field test, the naked mole-rat spent less time in the center of the field than C57/Bl6 mice.
As research in the naked mole-rat continues, it may become more common to study their cognitive abilities and motor skills, as the possibility may exist that they will become useful in the study of disease associated with old age, such as Alzheimer’s disease.
What do you think?
Do behavioral tests in naked mole-rats demonstrate their potential as laboratory models?
Deacon RM, Dulu TD, Patel NB. (2012). Naked mole-rats: behavioural phenotyping and comparison with C57BL/6 mice. Behav Brain Res. May 16;231(1):193-200.
Park TJ, Lu Y, Jüttner R, Smith ES, Hu J, Brand A, Wetzel C, Milenkovic N, Erdmann B, Heppenstall PA, Laurito CE, Wilson SP, Lewin GR. (2008). Selective inflammatory pain insensitivity in the African naked mole-rat (Heterocephalus glaber). PLoS Biol. Jan;6(1):e13.
Peterson BL, Park TJ, Larson J. (2012). Adult naked mole-rat brain retains the NMDA receptor subunit GluN2D associated with hypoxia tolerance in neonatal mammals. Neurosci Lett. Jan 11;506(2):342-5.