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
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences