Vorlesen Male dung beetles of the species Onthophagus taurus invest either in muscle strength or in testicle size? depending on which reproductive strategy they are following. Biologists have found that out by experimenting with these insects. Accordingly, horny beetles, which actively fight for females, develop particularly strong muscles with good food supply. In the case of unhatched beetles, on the other hand, the size of the testicles increases. an indicator of particularly fit sperm. The reason: The unheard males would be inferior to the horned competitors in direct combat, but take every opportunity to mate a female yet. If they succeed, their sperm will outperform their armed competitors, according to Robert Knell of the University of London and Leigh Simmons of the University of Western Australia. In some dung beetle species, the males come in two different forms: either as a horned fighter guarding his selected females and defending against other bugs, or as a hornless creep trying to seduce a female when the fighter is employed elsewhere. For the fighter, as much muscular strength as possible is crucial to the reproductive success, while the stalker is most likely to produce progeny when his sperm can assert themselves against the fighter's sperm. He mates his females several times, while the Schleicher must be happy if he ever comes to the course.

In their experiments, the scientists divided the hornless and the horned beetles into two groups: the first group received a normal food ration? a teaspoon of cow dung? for a period of five days. The beetles in the second group had to settle for a nutrient-poor portion. After five days passed, the researchers measured the muscle strength and weight of the testes of all beetles. As it turned out, all the animals in the malnourished group had lost body mass, but in different places: the weight of the testicles had decreased in the hornless beetles, while in the horned beetles the muscular strength had decreased.

Conversely, this means that the horned beetles put part of the nutrients absorbed through the diet into the development of muscle power. By contrast, their hornless peers use the resources needed to develop the testicles, concentrating on a strategy that compensates for their physical inferiority: they produce particularly fit sperm that can assert themselves against the sperm of the fierce competitors.

Robert Knell (University of London) and Leigh Simmons (University of Western Australia): Proceedings of the Royal Society B, online pre-release, doi: 10.1098 / rspb.2010.0257 ddp / science.de? Thomas Neuenschwander advertisement

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