Mole rats — tiny, hairless, wrinkled rodents from Africa –have recently come under intense scrutiny in Cornell’s biology labs.
These subterranean animals have drawn attention because of their relatively long lives; they are by far the oldest small rodents held in captivity. While most rodents of approximately the same size live for only three years, mole rats can live up to ten times that long. In labs, many are over 20 years old and some are as old as 26.
“[Cornell labs] have six colonies, each ranging from 15 to 35 individuals,” they live in plexiglass systems that simulate the underground tunnels the mole rats inhabit in nature, according to Dara Neuman ’03.
The life spans of the Heterocephalus glaber mole rats are not interesting in and of themselves, however. Mole rats are significant to Cornell researchers because they effectively demonstrate the theory of senescence.
This theory attempts to explain why some organisms’ bodies tend to last longer than others. The term senescence means the process of bodily deterioration that occurs with increasing age, manifested by an increased susceptibility to diseases and a decreasing ability to repair damage.
In other words, it is the natural breakdown of the parts of the body throughout an organism’s lifespan.
“Whatever kind of organism it is, it’s going to senesce,” said Prof. Paul Sherman, neurobiology and behavior, as reported by the Cornell News Service. “Of course, good food and exercise, proper medical care and avoiding risky behaviors may extend lives a bit. But nothing we can do in our lifetimes or many more to come is likely to stop senescence,” Sherman said.
The theory of senescence is based in evolutionary biology. The time when senescence begins to take effect is an inherited trait, and therefore evolves within a population. Populations with low rates of mortality from factor other than senescence tend to show later senescence. That is, the deterioration of the body tends to start later in organisms that are not frequently killed off by outside causes, according to researchers.
“Most people attribute aging solely to wear-and-tear on individuals’ bodies. We know about oxidative damage to DNA and cells, so we tend to say things like, ‘He died because his heart failed.’ True, that’s the proximate cause of death, but it doesn’t explain why a person’s heart lasts much longer than a gerbil’s heart. Senescence theory does: Long before a particular man or gerbil was born, natural selection had acted on the genomes of their species to cause gerbils’ bodies to senesce more rapidly than humans’ bodies,” Sherman said.
In November, The Journal of Zoology will publish an article by Sherman and Jennifer U.M. Jarvis entitled “Extraordinary life spans of naked mole-rats.”
Research on the theory of senescence is not the only research being carried out on mole rats at Cornell.
Neuman is part of a team studying communication between mole rats.
“They live in a colony kind of like honeybees. Mole rats were one of the first mammals found to do this,” she said.
The colony consists of one female queen and additional worker mole rats that forage for food underground. The rodents are known to communicate about both the quality of and distance to food.
“At first we thought maybe they had a dance like the honeybee, but there was no observable difference in their behavior when they found a good piece of food from when it was poor quality,” Neuman said.
It is now believed that mole rats possibly communicate chemically through smell, since food scouts seem to receive more attention after they have found a piece of good quality food as opposed to a poor quality piece.
Archived article by Elizabeth Donald