Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mole-rat Methuselahs push evolutionary theory of aging

07.11.2002


RESPECT FOR AN ELDER. Twenty-one-year-old Dara Neuman, a senior majoring in biology in Cornell’s College of Arts and Sciences, displays a naked mole-rat that was born years before she was. The extreme longevity of the rodents is said to help confirm the evolutionary theory of senescence
Cornell University Photography
Copyright © Cornell University


Virtually hairless, venerably wrinkled and very nearly blind, naked mole-rats -- those homely rodents from underground Africa -- remind some zoo-goers of little old men.

The resemblance is more than coincidence. They really are really old males -- and females, too -- biologists report in an article scheduled for November publication in the Journal of Zoology (Vol. 258, Part 3). Many naked mole-rats (Heterocephalus glaber) in laboratory colonies in the United States and South Africa have lived more than 20 years, and some are at least 26 years old, making them by far the oldest small rodents in captivity.

That distinction won’t get them birthday greetings from the president. But their species is being hailed as a perfect exemplar for the evolutionary theory of senescence (or aging), which explains why some bodies wear out before others. Senescence theory also tries to explain, for example, why gerbils live only a couple of years, humans regularly live eight to nine decades and redwood trees for millennia.



"Whatever kind of organism it is, it’s going to senesce," says Paul Sherman, a professor of neurobiology and behavior at Cornell University. "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." Evolutionary biologists define the term as the persistent decline in fitness components with age, due to internal physiological deterioration.

In the paper, "Extraordinary life spans of naked mole-rats," Sherman and his South African colleague Jennifer U.M. Jarvis report that laboratory mole-rats have survived nearly three decades, making their life spans about 10 times longer than other similar-size rodents. "Life spans of naked mole-rats offer strong support for evolutionary theories of aging," Sherman notes.

Evolutionary biologists agree there are two types of causes for the end of life. The proximate (or immediate) cause, such as drowning or essential body parts wearing out, gets reported in newspaper obituaries, whereas the ultimate (or long-term) cause, the genetic explanation for death, gets discussed in scholarly scientific papers, and Sherman offers this explanation for the difference:

"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 lasted 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.

"Proximate and ultimate explanations for senescence are not alternative, they are complementary," Sherman adds. "The first identifies specific physiological mechanisms whose breakdown results in senescence. The second explains how natural selection has acted to maintain or fail to maintain those mechanisms."

The Cornell researcher has studied colonies of naked mole-rats living in transparent plastic tunnel systems in his laboratory since 1979, first at the University of California-Berkeley and then in Ithaca. Jarvis has done the same for her mole-rats at the University of Cape Town. The animal-care protocols they pioneered have helped zookeepers worldwide to display the intriguing creatures for the education of the general public.

In nature, naked mole-rats are known to live at least 10 years. "We think they live longer in the laboratory than they do in the wild because they’re safer here, but they’re pretty safe in nature, too," Sherman says. One of the factors contributing to the evolution of longer life spans is reduced extrinsic mortality, which Sherman defines as causes of death that are outside an animal’s control, such as drowning in a flash flood or being devoured by a snake. In nature, naked mole-rats are largely protected from sources of extrinsic mortality by inhabiting subterranean burrows in extremely hard soils. Protection is enhanced by cooperative defense against predators. As a result, naked mole-rats have evolved genetic traits that make them more resistant to senescence than similar-sized, solitary, surface-dwelling rodents. Indeed, the only rodent known to live as long as the naked mole-rat is the African porcupine Hystrix brachyura , which is protected by its large body size and quills.

The diminutive naked mole-rat has something else going for it: greater fecundity with advancing age. "A large, old breeding female mole-rat gives birth to an incredible number of young and continues to do so year after year," Sherman says. "Our record for a laboratory female is 28 pups in one litter and more than 900 pups in a lifetime." Fecundity seems related to body size, Sherman adds, noting that mole-rat queens, like queens in honeybees and termites, are considerably larger than workers in their colonies. Fecundity is important because if old individuals can make disproportionate reproductive contributions, there will be strong selection to postpone senescence.

While naked mole-rats are models that support senescence theory, they are not perfect role models for humans. Senescence occurs, simultaneously, on all aspects of any organism, which means there is no single gene for aging or for youth. "Senescence theory," says Sherman, "tells us why the fountain of youth still eludes us -- and probably always will."

Roger Segelken | EurekAlert!
Further information:
http://www.news.cornell.edu/releases/Nov02/old_moles.hrs.html

More articles from Life Sciences:

nachricht Single-stranded DNA and RNA origami go live
15.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard

nachricht New antbird species discovered in Peru by LSU ornithologists
15.12.2017 | Louisiana State University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>