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naked mole-rat
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{{pp-semi-indef|small=yes}}{{short description|Burrowing rodent; one of only two known eusocial mammals}}{{Speciesbox| name = Naked mole-rat
4.3Pliocene - RecentHETEROCEPHALUS GLABER DATE=26 DECEMBER 2002, 10.1644/0.706.1, | image = Nacktmull.jpg| status = LC| status_system = IUCN3.1Heterocephalus glaber. The IUCN Red List of Threatened Species 2016 (errata version published in 2017). {{DOI>10.2305/IUCN.UK.2016-3.RLTS.T9987A22184136.en}}| display_parents = 2| grandparent_authority = Landry, 1957; Patterson, 2014| parent_authority = Rüppell, 1842| taxon = Heterocephalus glaberEduard Rüppell>Rüppell, 1842| range_map = Heterocephalus glaber dis.png| range_map_caption = Distribution of the naked mole-rat}}(File:Heterocephalus glaber June 2019.webm|thumb|Various aged naked mole-rats.)The naked mole-rat (Heterocephalus glaber), also known as the sand puppy,BOOK, Jonathan, Kingdon, vanc, East African Mammals: An Atlas of Evolution in Africa, Volume 2, Part B: Hares and Rodents,weblink 1 July 1984, University of Chicago Press, 978-0-226-43720-0, 489, is a burrowing rodent native to parts of East Africa. It is closely related to the blesmols and is the only species in the genus Heterocephalus of the family Heterocephalidae.{{MSW3 Hystricognathi | id = 13400041 | pages = 1542}} The naked mole-rat and the Damaraland mole-rat (Fukomys damarensis)BOOK, O'Riain, M. Justin, Faulkes, Chris G., vanc, 2008, African mole rats: eusociality, relatedness and ecological constraints, Judith, Korb, Jörgen, Heinze, Ecology of Social Evolution, 207–223, 10.1007/978-3-540-75957-7_10, 978-3-540-75956-0, Springer, JOURNAL, Burland TM, Bennett NC, Jarvis JU, Faulkes CG, Eusociality in African mole-rats: new insights from patterns of genetic relatedness in the Damaraland mole-rat (Cryptomys damarensis), Proceedings. Biological Sciences, 269, 1495, 1025–30, May 2002, 12028759, 1690998, 10.1098/rspb.2002.1978, are the only known eusocial mammals, the highest classification of sociality. It has a highly unusual set of physical traits that allow it to thrive in a harsh underground environment and is the only mammalian thermoconformer, almost entirely ectothermic (cold-blooded) in how it regulates body temperature.WEB,weblink Naked Mole Rat Genome May Hold Key to Long Life, Human Health & Longevity, LiveScience, Jennifer, Welsh, vanc, 2011-10-12, 2013-03-23, The naked mole-rat lacks pain sensitivity in its skin, and has very low metabolic and respiratory rates. While formerly considered to belong to the same family as other African mole-rats, Bathyergidae, more recent investigation places it in a separate family, Heterocephalidae.JOURNAL, Patterson, Bruce D., Upham, Nathan S., vanc, A newly recognized family from the Horn of Africa, the Heterocephalidae (Rodentia: Ctenohystrica), Zoological Journal of the Linnean Society, 172, 4, 942–963, December 2014, 10.1111/zoj.12201, BOOK,weblink The Kingdon Field Guide to African Mammals: Second Edition, Kingdon, Jonathan, vanc, Princeton University Press, 2015, 978-1472925312, Princeton, N.J., 224, BOOK, Wilson, Don E., Thomas E., Lacher, Russell A., Mittermeier, vanc, Handbook of the Mammals of the World Volume 6: Lagomorphs and Rodents, 2016, 312, Lynx Edicions, Barcelona, 978-8494189234, The naked mole-rat is also remarkable for its longevity and its resistance to cancer and oxygen deprivation.

Description

Typical individuals are {{convert|8|to|10|cm|in|0|abbr=on}} long and weigh {{convert|30|to|35|g|oz}}. Queens are larger and may weigh well over {{convert|50|g|oz}}, the largest reaching {{convert|80|g|oz}}. They are well-adapted to their underground existence. Their eyes are quite small, and their visual acuity is poor. Their legs are thin and short; however, they are highly adept at moving underground and can move backward as fast as they can move forward. Their large, protruding teeth are used to dig and their lips are sealed just behind the teeth, preventing soil from filling their mouths while digging.WEB,weblink Naked Mole-Rat, Meet Our Animals, Smithsonian National Zoo Park, yes,weblink" title="web.archive.org/web/20150426144754weblink">weblink 2015-04-26, About a quarter of their musculature is used in the closing of their jaws while they dig—about the same proportion that is utilized in the human leg.{{citation needed|date=June 2015}} They have little hair (hence the common name) and wrinkled pink or yellowish skin. They lack an insulating layer in the skin.

Physiology

Metabolism and respiration

The naked mole-rat is well adapted to the limited availability of oxygen within the tunnels of its typical habitat. It has underdeveloped lungs and its hemoglobin has a high affinity for oxygen, increasing the efficiency of oxygen uptake.JOURNAL, Maina, J.N., Maloiy, G.M.O., Makanya, A.N., Morphology and morphometry of the lungs of two East African mole rats, Tachyoryctes splendens and Heterocephalus glaber (Mammalia, Rodentia), Zoomorphology, September 1992, 112, 3, 167–179, 10.1007/BF01633107, JOURNAL, Park TJ, Reznick J, Peterson BL, Blass G, Omerbašić D, Bennett NC, Kuich PH, Zasada C, Browe BM, Hamann W, Applegate DT, Radke MH, Kosten T, Lutermann H, Gavaghan V, Eigenbrod O, Bégay V, Amoroso VG, Govind V, Minshall RD, Smith ES, Larson J, Gotthardt M, Kempa S, Lewin GR, Fructose-driven glycolysis supports anoxia resistance in the naked mole-rat, Science, 356, 6335, 307–311, April 2017, 28428423, 10.1126/science.aab3896, 2017Sci...356..307P, Guarino, Ben (April 23, 2017) Naked mole-rats are now even weirder: Without oxygen, they live like plants. The Washington Post. This reference makes some incorrect statements, such as implying that using glucose requires oxygen but using fructose does not. It has a very low respiration and metabolic rate for an animal of its size, about 70% that of a mouse, thus using oxygen minimally.JOURNAL, Buffenstein, Rochelle, The Naked Mole-Rat: A New Long-Living Model for Human Aging Research, (The Journals of Gerontology, The Journals of Gerontology: Series A), 1 November 2015, 60, 11, 1369–1377, 10.1093/gerona/60.11.1369, In response to long periods of hunger, its metabolic rate can be reduced by up to 25 percent.The naked mole-rat survives for at least 5 hours in air that contains only 5% oxygen; it does not show any significant signs of distress and continues normal activity. It can live in an atmosphere of 80% {{chem|CO|2}} and 20% oxygen. In zero-oxygen atmosphere, it can survive 18 minutes apparently without suffering any harm (but none survived a test of 30 minutes). During the anoxic period it loses consciousness, its heart rate drops from about 200 to 50 beats per minute, and breathing stops apart from sporadic breathing attempts. When deprived of oxygen, the animal uses fructose in its anaerobic glycolysis, producing lactic acid. This pathway is not inhibited by acidosis as happens with glycolysis of glucose. As of April 2017, it was not known how the naked mole-rat survives acidosis without tissue damage.JOURNAL, Storz JF, McClelland GB, Rewiring metabolism under oxygen deprivation, Science, 356, 6335, 248–249, April 2017, 28428384, 10.1126/science.aan1505, 2017Sci...356..248S,

Thermoregulation

The naked mole-rat does not regulate its body temperature in typical mammalian fashion. They are thermoconformers rather than thermoregulators in that, unlike other mammals, body temperature tracks ambient temperatures. However, it has also been claimed that "the Naked Mole-Rat has a distinct temperature and activity rhythm that is not coupled to environmental conditions."WEB, DataScience.com,weblink 2014, Uncovering the secrets of the naked mole-rat, February 9, 2015, The relationship between oxygen consumption and ambient temperature switches from a typical poikilothermic pattern to a homeothermic mode when temperature is at 28 Â°C or higher.JOURNAL, Daly TJ, Williams LA, Buffenstein R, Catecholaminergic innervation of interscapular brown adipose tissue in the naked mole-rat (Heterocephalus glaber), Journal of Anatomy, 190 ( Pt 3), 3, 321–6, April 1997, 9147219, 1467613, 10.1046/j.1469-7580.1997.19030321.x, At lower temperatures, naked mole-rats can use behavioral thermoregulation. For example, cold naked mole-rats huddle together or seek shallow parts of the burrows that are warmed by the sun. Conversely, when they get too hot, naked mole-rats retreat to the deeper, cooler parts of the burrows.

Pain insensitivity

(File:Naked Mole Rats-cropped.jpg|thumb|right|Captive naked mole-rats huddling together)The skin of naked mole-rats lacks neurotransmitters in their cutaneous sensory fibers. As a result, the naked mole-rats feel no pain when they are exposed to acid or capsaicin. When they are injected with substance P, a type of neurotransmitter, the pain signaling works as it does in other mammals but only with capsaicin and not with acids. This is proposed to be an adaptation to the animal living in high levels of carbon dioxide due to poorly ventilated living spaces which would cause acid to build up in their body tissues.JOURNAL, 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, Selective inflammatory pain insensitivity in the African naked mole-rat (Heterocephalus glaber), PLoS Biology, 6, 1, e13, January 2008, 18232734, 2214810, 10.1371/journal.pbio.0060013, Naked mole-rats' substance P deficiency has also been tied to their lack of the histamine-induced itching and scratching behavior typical of rodents.JOURNAL, Smith ES, Blass GR, Lewin GR, Park TJ, Absence of histamine-induced itch in the African naked mole-rat and "rescue" by Substance P, Molecular Pain, 6, 1, 1744–8069–6–29, May 2010, 20497578, 2886013, 10.1186/1744-8069-6-29,

Resistance to cancer

Naked mole-rats have a high resistance to tumours, although it is likely that they are not entirely immune to related disorders.JOURNAL, Delaney MA, Ward JM, Walsh TF, Chinnadurai SK, Kerns K, Kinsel MJ, Treuting PM, Initial Case Reports of Cancer in Naked Mole-rats (Heterocephalus glaber), Veterinary Pathology, 53, 3, 691–6, May 2016, 26846576, 10.1177/0300985816630796, A potential mechanism that averts cancer is an "over-crowding" gene, p16, which prevents cell division once individual cells come into contact (known as "contact inhibition"). The cells of most mammals, including naked mole-rats, undergo contact inhibition via the gene p27 which prevents cellular reproduction at a much higher cell density than p16 does. The combination of p16 and p27 in naked mole-rat cells is a double barrier to uncontrolled cell proliferation, one of the hallmarks of cancer.JOURNAL, Seluanov A, Hine C, Azpurua J, Feigenson M, Bozzella M, Mao Z, Catania KC, Gorbunova V, Hypersensitivity to contact inhibition provides a clue to cancer resistance of naked mole-rat, Proceedings of the National Academy of Sciences of the United States of America, 106, 46, 19352–7, November 2009, 19858485, 2780760, 10.1073/pnas.0905252106, 2009PNAS..10619352S, In 2013, scientists reported that the reason naked mole-rats do not get cancer can be attributed to an "extremely high-molecular-mass hyaluronan" (HMW-HA) (a natural sugary substance), which is over "five times larger" than that in cancer-prone humans and cancer-susceptible laboratory animals.NEWS, Zimmer, Carl, vanc, A Homely Rodent May Hold Cancer-Fighting Clues,weblink 19 June 2013, New York Times, 20 June 2013, JOURNAL, Callaway, Ewen, Simple molecule prevents mole rats from getting cancer, Nature, 19 June 2013, 10.1038/nature.2013.13236, NEWS, Naked mole-rat gives cancer clues, Briggs H,weblink BBC News, 19 June 2013, 21 June 2013, The scientific report was published a month later as the cover story of the journal Nature.JOURNAL, Tian X, Azpurua J, Hine C, Vaidya A, Myakishev-Rempel M, Ablaeva J, Mao Z, Nevo E, Gorbunova V, Seluanov A, High-molecular-mass hyaluronan mediates the cancer resistance of the naked mole rat, Nature, 499, 7458, 346–9, July 2013, 23783513, 3720720, 10.1038/nature12234, 2013Natur.499..346T, A few months later, the same University of Rochester research team announced that naked mole-rats have ribosomes that produce extremely error-free proteins.JOURNAL, Azpurua J, Ke Z, Chen IX, Zhang Q, Ermolenko DN, Zhang ZD, Gorbunova V, Seluanov A, Naked mole-rat has increased translational fidelity compared with the mouse, as well as a unique 28S ribosomal RNA cleavage, Proceedings of the National Academy of Sciences of the United States of America, 110, 43, 17350–5, October 2013, 24082110, 3808608, 10.1073/pnas.1313473110, 2013PNAS..11017350A, Because of both of these discoveries, the journal Science named the naked mole-rat "Vertebrate of the Year" for 2013.JOURNAL, Breakthrough of the year 2013. Notable developments, Science, 342, 6165, 1435–41, December 2013, 24357296, 10.1126/science.342.6165.1444, In 2016, a report was published that recorded the first ever discovered malignancies in two naked mole-rats, in two individuals.JOURNAL, Delaney MA, Ward JM, Walsh TF, Chinnadurai SK, Kerns K, Kinsel MJ, Treuting PM, Initial Case Reports of Cancer in Naked Mole-rats (Heterocephalus glaber), Veterinary Pathology, 53, 3, 691–6, May 2016, 26846576, 10.1177/0300985816630796,weblink NEWS, St. Fleur, Nicholas, vanc, Two Naked Mole Rats, Seemingly Immune to Cancer, Got Cancer,weblink February 19, 2016, New York Times, February 20, 2016, WEB, Grens K, 2016, Cancer detected in naked mole rats, The Scientist,weblink February 15, 2016, However, both naked mole-rats were captive-born at zoos, and hence lived in an environment with 21% atmospheric oxygen compared to their natural 2–9%, which may have promoted tumorigenesis.JOURNAL, Welsh JS, Traum TL, Regarding Mole Rats and Cancer, Veterinary Pathology, 53, 6, 1264–1265, November 2016, 27733703, 10.1177/0300985816646434, The Golan Heights blind mole-rat (Spalax golani) and the Judean Mountains blind mole-rat (Spalax judaei) are also resistant to cancer, but by a different mechanism.JOURNAL, Cormier, Zoe, Blind mole rats may hold key to cancer, Nature, 5 November 2012, 10.1038/nature.2012.11741,

Longevity

The naked mole-rat is also of interest because it is extraordinarily long-lived for a rodent of its size (up to 32 yearsWEB,weblink genomics.senescence.info, Naked mole-rat (Heterocephalus glaber) longevity, ageing, and life history, 2013-11-07, ) and holds the record for the longest living rodent.JOURNAL, Buffenstein R, Jarvis JU, The naked mole rat--a new record for the oldest living rodent, Science of Aging Knowledge Environment, 2002, 21, 7pe–7, May 2002, 14602989, 10.1126/sageke.2002.21.pe7, The mortality rate of the species does not increase with age, and thus does not conform to that of most mammals (as frequently defined by the Gompertz-Makeham law of mortality).JOURNAL, Ruby JG, Smith M, Buffenstein R, Naked Mole-Rat mortality rates defy gompertzian laws by not increasing with age, eLife, 7, January 2018, 29364116, 5783610, 10.7554/eLife.31157, Naked mole-rats are highly resistant to cancerJOURNAL, Buffenstein R, Negligible senescence in the longest living rodent, the naked mole-rat: insights from a successfully aging species, Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology, 178, 4, 439–45, May 2008, 18180931, 10.1007/s00360-007-0237-5, and maintain healthy vascular function longer in their lifespan than shorter-living rats.JOURNAL, Csiszar A, Labinskyy N, Orosz Z, Xiangmin Z, Buffenstein R, Ungvari Z, Vascular aging in the longest-living rodent, the naked mole rat, American Journal of Physiology. Heart and Circulatory Physiology, 293, 2, H919–27, August 2007, 17468332, 10.1152/ajpheart.01287.2006, The reason for their longevity is debated, but is thought to be related to their ability to substantially reduce their metabolism during hard times, and so prevent aging-induced damage from oxidative stress. This has been referred to as "living their life in pulses".WEB,weblink Ugly Duckling Mole Rats Might Hold Key To Longevity, Sciencedaily.com, 2007-10-16, 2009-03-11, Their longevity has also been attributed to "protein stability".JOURNAL, Pérez VI, Buffenstein R, Masamsetti V, Leonard S, Salmon AB, Mele J, Andziak B, Yang T, Edrey Y, Friguet B, Ward W, Richardson A, Chaudhuri A, Protein stability and resistance to oxidative stress are determinants of longevity in the longest-living rodent, the naked mole-rat, Proceedings of the National Academy of Sciences of the United States of America, 106, 9, 3059–64, March 2009, 19223593, 2651236, 10.1073/pnas.0809620106, 2009PNAS..106.3059P, Because of their extraordinary longevity, an international effort was put into place to sequence the genome of the naked mole-rat.WEB,weblink Proposal to Sequence an Organism of Unique Interest for Research on Aging: Heterocephalus glaber, the Naked Mole-Rat, Genomics.senescence.info, 2009-04-30, A draft genome was made available in 2011WEB,weblink Naked Mole-Rat Database, Naked Mole-Rat Database 2011, 5 July 2011, WEB,weblink Naked Mole-Rat Genome Resource, Naked Mole-Rat Genome Resource 2011, 5 July 2011, JOURNAL, Kim EB, Fang X, Fushan AA, Huang Z, Lobanov AV, Han L, Marino SM, Sun X, Turanov AA, Yang P, Yim SH, Zhao X, Kasaikina MV, Stoletzki N, Peng C, Polak P, Xiong Z, Kiezun A, Zhu Y, Chen Y, Kryukov GV, Zhang Q, Peshkin L, Yang L, Bronson RT, Buffenstein R, Wang B, Han C, Li Q, Chen L, Zhao W, Sunyaev SR, Park TJ, Zhang G, Wang J, Gladyshev VN, Genome sequencing reveals insights into physiology and longevity of the naked mole rat, Nature, 479, 7372, 223–7, October 2011, 21993625, 3319411, 10.1038/nature10533, 2011Natur.479..223K, with an improved version released in 2014.JOURNAL, Keane M, Craig T, Alföldi J, Berlin AM, Johnson J, Seluanov A, Gorbunova V, Di Palma F, Lindblad-Toh K, Church GM, de Magalhães JP, The Naked Mole Rat Genome Resource: facilitating analyses of cancer and longevity-related adaptations, Bioinformatics, 30, 24, 3558–60, December 2014, 25172923, 4253829, 10.1093/bioinformatics/btu579, ts karyotype has 2n = 60. Further transcriptome sequencing revealed genes related to mitochondria and oxidation reduction processes to have high expression levels in the naked mole-rat when compared to mice, which may contribute to their longevity.JOURNAL, Yu C, Li Y, Holmes A, Szafranski K, Faulkes CG, Coen CW, Buffenstein R, Platzer M, de Magalhães JP, Church GM, RNA sequencing reveals differential expression of mitochondrial and oxidation reduction genes in the long-lived naked mole-rat when compared to mice, PLOS One, 6, 11, e26729, 2011, 22073188, 3207814, 10.1371/journal.pone.0026729, 2011PLoSO...626729Y, The DNA repair transcriptomes of the liver of humans, naked mole rats and mice were compared.JOURNAL, MacRae SL, Croken MM, Calder RB, Aliper A, Milholland B, White RR, Zhavoronkov A, Gladyshev VN, Seluanov A, Gorbunova V, Zhang ZD, Vijg J, DNA repair in species with extreme lifespan differences, Aging, 7, 12, 1171–84, December 2015, 26729707, 4712340, 10.18632/aging.100866, The maximum lifespans of humans, naked mole rats, and mice are respectively c. 120, 30 and 3 years. The longer-lived species, humans and naked mole rats, expressed DNA repair genes, including core genes in several DNA repair pathways, 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 facilitates greater longevity, and also are consistent with the DNA damage theory of aging.Bernstein H, Payne CM, Bernstein C, Garewal H, Dvorak K (2008). "Cancer and aging as consequences of un-repaired DNA damage". In: New Research on DNA Damages (Editors: Honoka Kimura and Aoi Suzuki) Nova Science Publishers, Inc., New York, Chapter 1, pp. 1-47. open access, but read only {{ISBN|1604565810}} {{ISBN|978-1604565812}}

Size

Reproducing females become the dominant female, usually, by founding new colonies, fighting for the dominant position, or taking over once the reproducing female dies. These reproducing females tend to have longer bodies than that of their non-reproducing counterparts of the same skull width. The measurements of females before they became reproductive and after show significant increases in body size. It is believed that this trait does not occur due to pre-existing morphological differences but to the actual attainment of the dominant female position.JOURNAL, Young AJ, Bennett NC, Morphological divergence of breeders and helpers in wild Damaraland mole-rat societies, Evolution; International Journal of Organic Evolution, 64, 11, 3190–7, November 2010, 20561049, 10.1111/j.1558-5646.2010.01066.x, As with the reproductive females, the reproductive males also appear to be bigger in size than their non-reproducing counterparts but not as much so as in the case of the females. These males also have visible outlines of the testes through the skin of their abdomens. Unlike the females, there are usually multiple reproducing males.JOURNAL, Jarvis JU, Bennett NC, 1993, Eusociality has evolved independently in two genera of bathyergid mole-rats — but occurs in no other subterranean mammal, Behavioral Ecology and Sociobiology, 33, 4, 253–260, 10.1007/bf02027122,

Chronobiology

The naked mole-rat's subterranean habitat imposes constraints on its circadian rhythm.BOOK, 10.1016/b978-0-08-045337-8.00152-2, Naked Mole Rats: Their Extraordinary Sensory World, Encyclopedia of Animal Behavior, 505–512, 2010, Park, T.J., Lewin, G.R., Buffenstein, R., 978-0-08-045337-8, Living in constant darkness, most individuals possess a free-running activity pattern and are active both day and night, sleeping for short periods of time several times in between.

Ecology and behavior

Distribution and habitat

The naked mole-rat is native to the drier parts of the tropical grasslands of East Africa, predominantly southern Ethiopia, Kenya, and Somalia.BOOK, Sherman, Paul W., Jennifer, Jarvis, Richard, Alexander, vanc, The Biology of the Naked Mole-rat, 1991, Princeton University Press, Princeton, N.J., 978-0691024486, Clusters averaging 75 to 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 three to five kilometres (2–3 mi) in cumulative length.BOOK, Dawkins, Richard, vanc, 1976, 2006, 30th anniversary, The Selfish Gene, Oxford University Press, 978-0-19-286092-7,

Roles

The naked mole-rat is the first mammal discovered to exhibit eusociality. This eusocial structure is similar to that found in ants, termites, and some bees and wasps.JOURNAL, Jarvis, Jennifer, vanc, Eusociality in a Mammal: Cooperative Breeding in Naked Mole-Rat Colonies, Science, May 1981, 212, 4494, 571–573, 1686202, 10.1126/science.7209555, 1981Sci...212..571J, WEB, Marshall, Michael, vanc, Eight ugly animals we should save anyway, BBC Earth, 17 October 2014,weblink 3 January 2015, Only one female (the queen) and one to three males reproduce, while the rest of the members of the colony function as workers.JOURNAL, Sherman, Paul W., Jarvis, Jennifer U. M., Braude, Stanton H., August 1992, Naked Mole Rats, Scientific American, 267, 2, 72–79, 24939178, 10.1038/scientificamerican0892-72, The queen and breeding males are able to breed at one year of age. Workers are sterile, with the smaller focusing on gathering food and maintaining the nest, while larger workers are more reactive in case of attack. The non-reproducing females appear to be reproductively suppressed, meaning the ovaries do not fully mature, and do not have the same levels of certain hormones as the reproducing females. On the other hand, there is little difference of hormone concentration between reproducing and non-reproducing males. In experiments where the reproductive female was removed or died, one of the non-reproducing females would take over and become sexually active. Non-reproducing members of the colony are involved in cooperative care of the pups produced by the reproducing female. This occurs through the workers keeping the pups from straying, foraging for food, grooming, contributing to extension of tunnels, and keeping them warm.(File:Naked mole rat.jpg|thumb|Female mole-rat)The Damaraland mole-rat (Cryptomys damarensis) is the only other eusocial mammal currently known.

Queen and gestation

The relationships between the queen and the breeding males may last for many years; other females are temporarily sterile. Queens live from 13 to 18 years, and are extremely hostile to other females behaving like queens, or producing hormones for becoming queens. When the queen dies, another female takes her place, sometimes after a violent struggle with her competitors. Once established, the new queen's body expands the space between the vertebrae in her backbone to become longer and ready to bear pups.WEB,weblink San Diego's Animals. Mammals: Naked Mole-rat, Sandiegozoo.org, 2013-03-23, Gestation is about 70 days. A litter typically ranges from three to twelve pups, but may be as large as twenty-eight. The average litter size is eleven.Counting mole-rat mammaries and hungry pups, biologists explain why naked rodents break the rules, Roger Segelken, Cornell News, August 9, 1999 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.BOOK, Ross, Piper, vanc, Ross Piper, Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press, Westport, Conn, 2007, 978-0-313-33922-6, The young are born blind and weigh about {{convert|2|g|oz|sigfig=1}}. The queen nurses them for the first month; after which the other members of the colony feed them fecal pap until they are old enough to eat solid food.

Workers

Smaller workers focus on acquiring food and maintaining tunnels, while the larger workers are more reactive in case of attacks.NEWS,weblink Meet the 'sabre-toothed sausage', Rebecca, Morelle, vanc, BBC News, May 5, 2010, As in certain bee species, the workers are divided along a continuum of different worker-caste behaviors instead of discrete groups. Some function primarily as tunnellers, expanding the large network of tunnels within the burrow system, and some primarily as soldiers, protecting the group from outside predators. There are two main types of worker, the "frequent workers" who frequently perform tasks such as foraging and nest building and "infrequent workers" that show role overlap with the "frequent workers" but perform at a much slower rate.JOURNAL, Jarvis JU, 1981, Eusociality in a Mammal: Cooperative Breeding in Naked Mole-Rat Colonies, Science, 212, 4494, 571–573, 1686202, 10.1126/science.7209555, 1981Sci...212..571J, Workers are sterile when there is no new reproductive role to fill.

Dispersers

Inbreeding is a common phenomenon among naked mole-rats within a colony. Prolonged inbreeding is usually associated with lower fitness.JOURNAL, Bengtsson, B.O., Avoiding inbreeding: at what cost?, Journal of Theoretical Biology, August 1978, 73, 3, 439–444, 10.1016/0022-5193(78)90151-0, However, the discovery of a disperser role has revealed an outbreeding mechanism in addition to inbreeding avoidance.JOURNAL, Bromham, Lindell, Harvey, Paul H, Behavioural ecology: Naked mole-rats on the move, Current Biology, September 1996, 6, 9, 1082–1083, 10.1016/S0960-9822(02)70671-4, 8805352, Dispersers are morphologically, physiologically as well as behaviorally distinct from colony members and actively seek to leave their burrow when an escape opportunity presents itself. These individuals are equipped with generous fat reserves for their journey. Though they possess high levels of luteinizing hormone, dispersers are only interested in mating with individuals from foreign colonies rather than their own colony's queen. They are also show little interest in working cooperatively with colony members in their natal burrow. Hence, the disperser morph is well-prepared to promote the exchange of individuals as well as genetic material between two otherwise separate colonies.

Colonies

Colonies range in size from 20 to 300 individuals, with an average of 75.The Naked Truth About Mole-Rats {{webarchive|url=https://web.archive.org/web/20090713154017weblink |date=2009-07-13 }}, Jill Locantore, Smithsonian Zoogoer, May/June 2002

Female mate choice

Reproductively active female naked mole rats tend to associate with unfamiliar males (usually non-kin), whereas reproductively inactive females do not discriminate.JOURNAL, Clarke FM, Faulkes CG, Kin discrimination and female mate choice in the naked mole-rat Heterocephalus glaber, Proceedings. Biological Sciences, 266, 1432, 1995–2002, October 1999, 10584337, 1690316, 10.1098/rspb.1999.0877, The preference of reproductively active females for unfamiliar males is interpreted as an adaptation for inbreeding avoidance. Inbreeding is avoided because it ordinarily leads to the expression of recessive deleterious alleles.JOURNAL, Charlesworth D, Willis JH, The genetics of inbreeding depression, Nature Reviews. Genetics, 10, 11, 783–96, November 2009, 19834483, 10.1038/nrg2664,

Diet

(File:Naked Mole Rat Eating.jpg|thumb|A captive naked mole-rat eating)Naked mole-rats feed primarily on very large tubers (weighing as much as a thousand times the body weight of a typical mole-rat) that they find deep underground through their mining operations. A single tuber can provide a colony with a long-term source of food—lasting for months, or even years, as they eat the inside but leave the outside, allowing the tuber to regenerate. Symbiotic bacteria in their intestines ferment the fibres, allowing otherwise indigestible cellulose to be turned into volatile fatty acids.Naked mole-rats sometimes also eat their own feces. This may be part of their eusocial behavior and a means of sharing hormones from the queen.JOURNAL, Reardon, Sara, Poo turns naked mole rats into better babysitters, Nature, 20 October 2015, 10.1038/nature.2015.18606,

Predators

Naked mole rats are primarily preyed upon by snakes—especially the Rufous beaked snake and Kenyan sand boa—as well as various raptors. They are at their most vulnerable when constructing mounds and ejecting soil to the surface.BOOK, Mammals of Africa, Volume III,weblink Bloomsbury Natural History, 670, February 2013, 9781408122570,

Conservation status

Naked mole-rats are not threatened. They are widespread and numerous in the drier regions of East Africa.International Union for Conservation of Nature Red List: Heterocephalus Glaber listed as "least concern".

References

Further reading

  • WEB


,weblink
, Heterocephalus glaber, naked mole rat
, Animal Diversity Web
, Deborah, Ciszek
, 1999, 22 January 2010
,
  • WEB


,weblink
, Heterocephalus glaber: Cooperation is Key
, Brookfield Zoo
, 22 January 2010
, yes
,weblink" title="web.archive.org/web/20101206175341weblink">weblink
, 6 December 2010
,
,
  • WEB


,weblink
, Naked Mole Rat
, Chicago Zoological Society
, 26 April 2017
,
  • WEB


,weblink
, Naked mole rat (Heterocephalus glaber) images
, Bioimages at Vanderbilt University
, 2003, Steve, Baskauf
, 22 January 2010
,
  • WEB


,weblink
, Naked Mole-rats Hold Clues to Human Aging
, October 2006, 22 January 2010
, Jeanna, Bryner, LiveScience
,
  • JOURNAL, Sherman, Paul W., Jarvis, Jennifer U. M., vanc, Extraordinary life spans of naked mole-rats (Heterocephalus glaber), Journal of Zoology, November 2002, 258, 3, 307–311, 10.1017/S0952836902001437,
  • JOURNAL, Tool use by naked mole-rats, Animal Cognition, 71–74, Gabriela, Shuster, P. W., Sherman, vanc, 1, 1, 1998, 10.1007/s100710050009,
  • WEB


,weblink
, Strange Creature Immune to Pain
, Charles Q., Choi, vanc
, LiveScience
, January 2008, 22 January 2010
,
  • WEB


,weblink
, Small Mammals (with a naked mole-rat webcam)
, Smithsonian National Zoological Park
, 22 January 2010
,

External links

{{Commons|Heterocephalus glaber|Naked Mole Rat}}{{Wikispecies|Heterocephalus glaber|Naked Mole Rat}}
  • {{UCSC genomes|hetGla2}}
{{Bathyergidae nav}}{{Taxonbar|from=Q276290}}


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