COLLEGE STATION – This is all underground, and naked mole-ratsprefer it that way: Momma naked mole-rat is the only one having babies,and she's got several naked mole-rat boyfriends.
Were it human, the family would argue it out on a national talkshow. As it is, the social behavior of these tiny rodents hasscientists intrigued, right down to their naked mole-rat molecules.
"African mole-rats are very good models for studying socialstructure. I'm interested in the genetic markers associated withstructure," said Colleen Ingram, whose doctoral degree will be bestowedFriday at Texas A&M University based on her findings about thecritters' parentage.
Ingram looked at regions of DNA - specifically the microsatellites,which represent distinct DNA bands, much like a satellite, whichseparate from the main DNA band. These rapidly changing regions of DNAdon't code for any particular trait, as far as scientists can tell.Ingram thought these regions shouldn't be overlooked.
"If there is a random-mating population, there are a lot of sizes ofthose DNA bands, but a child only gets one set from the mother and onefrom the father," Ingram noted. These markers are used in paternitycases for humans, she said.
She looked for changes in the processes and patterns of this strand in mole-rats, she said.
"The current methods of analyses of microsatellite markers areoversimplified and may lead to incorrect conclusions when looking atnatural populations and their social structures," Ingram said. "Therelationship among members of the mole-rat family are well-accepted.Some species (of mole-rat) are strictly solitary while others, such asthe naked mole-rat, are highly social."
DNA markers, like the satellites, are important because they canreveal how traits pass from one mother to her multitude of babiesconceived by various interrelated fathers. That may help understand whyscores of offspring in the family are willing to support the mothernaked mole-rat.
But first, naked mole-rats. They live in Somalia, Ethiopia andKenya. They are 3-6 inches long, have pink furless skin, tiny eyeswhich never see the light of day, and long front teeth for digging.Despite their tiny size, the naked mole-rat family den may stretch for2 miles entirely underground, with various rooms. In one room, a plantroot protrudes to provide a meal; in another is the "potty." When a newhallway is needed, usually for new food supplies, the naked mole-ratsiblings form an earth moving chain to pass dirt out a hole which lateris covered to block out intruders.
The most unusual room is the largest. It's where Momma nakedmole-rat produces more babies – as many as 12 at a time every couple ofmonths. Here she is stoked by her numerous mates and tended to by anynumber of offspring whose lot in life - if not to dig tunnels - is tokeep Momma happy.
This behavior is common – even accepted and marveled over – ininsects such as bees, termites and ants. But the naked mole-rat, amammal, is the most advanced species to live in this arrangement, saidDr. Rodney Honeycutt, Texas A&M Univeristy wildlife professor whose1992 article in American Scientist explained naked mole-rat life.
Scientists call it "eusocial" in that the young are cared for by thegroup, individuals in the group give up their ability to reproduce inorder to do other jobs, and there are at least two generations thatoverlap to do the family's work, Honeycutt noted.
Why don't teenaged naked mole-rats revolt and head for their own tunnel? That's where genetics may play a role.
"Biological evolution is generally seen as a competition, a contestamong individuals struggling to survive and reproduce," said Honeycutt,who was Ingram's lead professor and began studying mole-rats in theearly 1980s while at Harvard
"It runs counter to everything we know about evolution," Honeycuttsaid. "In fact, (Charles) Darwin himself said social animals representa real challenge to his theory (of natural selection and individualfitness)."
Honeycutt explained that after several generations of inbreeding,the offspring – say two sisters – may be more closely related to eachother than to the parents. They preserve themselves by helping motherproduce more offspring with their genetic makeup.
Knowing why animals exist with or without social structures could bemore far reaching than the intricate underground tunnels of the nakedmole-rat. What scientists learn about its genetic connection to socialbehavior could ultimately impact how endangered species, for example,are managed for survival, Ingram said. The fewer the animals of onespecies, the smaller its gene pool.
Ingram will continue her work with conservation genetics in her newposition at the American Museum of Natural History in New York.
The above story is based on materials provided by Texas A&M University - Agricultural Communications. Note: Materials may be edited for content and length.
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