Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stressed-out African naked mole-rats may provide environmental and genetic clues about infertility in humans

02.07.2007
A tiny, blind, hairless subterranean rodent that lives in social colonies in the harsh, semi-arid conditions of Africa could shed light on stress-related infertility in humans, the 23rd annual meeting of the European Society of Human Reproduction and Embryology will hear.

Dr Chris Faulkes, a senior lecturer at the School of Biological & Chemical Sciences, Queen Mary, University of London, will tell the conference that the African naked mole-rat is at the extreme end of a continuum of socially-induced reproductive suppression among mammals, with other examples including primates such as marmosets and tamarins, mongooses and members of the dog family (such as wolves and jackals).

The naked mole-rat lives in colonies of between 100-300 animals, but only the “queen” reproduces, suppressing fertility in both the females and the males around her by bullying them.

Dr Faulkes said: “The queen exerts her dominance over the colony by, literally, pushing the other members of the colony around. She ‘shoves’ them to show who’s boss. We believe that the stress induced in the lower-ranking animals by this behaviour affects their fertility. There appears to be a total block to puberty in almost all the non-breeding mole-rats so that their hormones are kept down and their reproductive tracts are under-developed.

“Currently, we think that the behavioural interactions between the queen and the non-breeders are translated into the suppression of certain fertility hormones (luteinizing and follicle stimulating hormones). In the non-breeding females this has the effect of suppressing the ovulatory cycle, while in the non-breeding males it causes lower testosterone concentrations, and lower numbers of sperm. In most non-breeding males, sperm that are present are non-motile.

“The queen also seems to exert control over the breeding males, so that concentrations of their testosterone are suppressed except when she is ready to mate.”

However, this stress-related block to fertility is reversible. When the queen dies, the other non-breeding, highest ranking females battle it out for dominance, with the winner rapidly becoming reproductively active.

“Studies of dominance within colonies have revealed that breeding animals have the highest social rank. Furthermore, concentrations of urinary testosterone, a hormone associated with aggression, in the queen and non-breeders of both sexes correlated significantly with rank position. In experiments where the queen is removed from her colony, reproductive activation in the female taking over as queen was accompanied by the development and expression of aggressive behaviour in the form of ‘shoving’. These succeeding females were also previously high ranking and had relatively high concentrations of urinary testosterone. This supports the hypothesis that the attainment and maintenance of reproductive status in the queen, and control of the social order of the colony, is related to dominance behaviour,” said Dr Faulkes.

Natural cues such as changes in day length and social stress act through areas of the brain that control reproduction and, as it is likely that such neuroendocrine pathways are similar across species, understanding how they work in naked mole-rats could lead to a better understanding of the mechanisms involved in some stress-related infertility in humans. Dr Faulkes said: “Social suppression of reproduction in marmoset monkeys is very similar to that in naked mole-rats, and as these are primates the applications to understanding human stress-related infertility aren't so far fetched.

“The neurobiological process underlying the way mammals respond to social and environmental cues are still largely unknown,” he continued. “In a wider comparative study of African mole-rat species, we are also researching into genes that may give rise to the quite different forms of social bonding and affiliative behaviours observed in mole-rats. Studies on voles by researchers in the US have shown that complex behaviours like monogamy and promiscuity can be influenced by single genes that differ among species in their patterns of expression in the brain.

“Humans also vary widely in the way in which they form social bonds with their partners, offspring and kin. By making careful comparisons with model species like mole-rats, we may be able to tease apart the relative contribution of genes, environment, up-bringing and culture to complex social behaviour in our own species.”

For the African naked mole-rat, the advantages of their social organisation mean that almost all the members of the colony are co-operating and directing their energies towards foraging for food in order for the whole community to survive, rather than indulging in physically exhausting mating and reproductive behaviour. The “workers” dig a network of tunnels, often several kilometres long, which they use to find their food of roots and tubers, while the “soldiers” defend the colony against foreign mole-rats and predators such as snakes.

“By living in large social groups with a co-operative non-breeding workforce, naked mole-rats are able to exploit an ecological niche where solitary animals or small groups would be unlikely to survive,” said Dr Faulkes.

Emma Mason | alfa
Further information:
http://www.mac.com

Further reports about: Faulkes colony concentrations dominance infertility naked non-breeding queen testosterone

More articles from Life Sciences:

nachricht How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>