Why does a male copulate without delivering semen? In a study that sheds new light on the evolution of sexual behaviour, researchers have utilised a novel technique to reveal that in feral chickens, the simple stimulus generated by male mounting reduces the sexual promiscuity of a hen, indicating that even copulations that do not result in semen transfer, a puzzling male behaviour frequently observed in the chicken and many other species, may be crucial to defend the paternity of a male.
Females of many species often copulate with multiple males, leading to the competition between the ejaculates of different males over fertilisation (sperm competition). Males are therefore selected to avoid sperm competition by preventing females from mating with other males. In a number of species, mostly insects, female promiscuity is temporarily reduced following copulation and this has been associated with highly specialised male insemination products. However, these paternity defence mechanisms typically require costly male investment in a female, and are at odds with the fact that males often copulate without delivering semen. Importantly, previous studies have not considered that female promiscuity may be inhibited by stimuli generated by the simple act of male mounting.
In a new study, a team of researchers from Stockholm University (Sweden), University of Sheffield and University of Oxford (UK) tested this idea in the sexually promiscuous chicken, using a novel technique that separates the effect of insemination products from that of mounting alone. The researchers detected the response of hens to the mounting of a rooster, by fitting some hens with a light plastic harness covering their cloaca, thus preventing insemination. The use of this technique demonstrated that mounting alone (independently of insemination) not only drastically inhibits the propensity of a hen to mate with a new rooster, but also reduces the number of sperm that she obtains from a new rooster in the 2-4 days following mounting. Therefore, roosters can defend their paternity by reducing the promiscuity of the hens that they have inseminated, by exploiting the hen’s response to the simple stimulus of mounting. Consistent with this idea, roosters often mount hens that they previously inseminated without delivering additional semen. Therefore, this study demonstrates that even though the ultimate function of sex is fertilisation, copulations resulting in the delivery of little or no sperm are not necessarily functionally meaningless but may have an important evolutionary significance.
Hanne Lovlie | alfa
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22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
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Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
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For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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