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Australian grasshopper gave up sex 250,000 years ago – and has no regrets

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On Earth, there are many species that consist of only females that breed without the participation of males. It is generally believed that this method of reproduction inevitably leads to negative consequences for the species. But a grasshopper living in Australia has shown that even after a quarter of a million years of life without males, nothing threatens the well-being of the species.

Biology

Most living beings on our planet have two sexes: male and female. This state of affairs seems natural and correct to us, but, as often happens in the wild, not always and not all species follow the beaten path, because there are many animal species in which intraspecific mating does not occur, but they do not die out, but safely still exist.

They continue their race through parthenogenesis, or “virgin reproduction”: unfertilized eggs develop in the bodies of females, from which new individuals are obtained, usually also females. Most often, invertebrate animals (for example, insects and crustaceans) reproduce by parthenogenesis, but it is also found in vertebrates: about 70 species are known, including lizards, frogs, and even some birds, in which reproduction occurs without the participation of male individuals. In mammals, such species are not known in nature, but under laboratory conditions, cubs have already been obtained from same-sex pairs of mice.

It is believed that this method of reproduction is unstable and loses in comparison with the usual sexual one: since daughters are, in fact, clones of their mothers, the genetic diversity of the species is extremely low, and if external conditions change, this can lead to the extinction of the species. However, nature once again decided to dispel our misconceptions: after eighteen years of studying the parthenogenetic grasshopper Warramaba virgo, scientists came to the conclusion that its species has existed for a quarter of a million years and is in no hurry to die out.

According to the results of the study, W. virgo was formed as a result of interspecific crossing of two other sexually reproducing species: W. flavolineata and W. whitei. Initially, scientists believed that the high viability of W. virgo was associated with repeated crosses of parental species and the effect of heterosis, in which hybrids have better characteristics than parental species (an eloquent example is the mule). However, a genetic study of all three species of grasshoppers has shown that this is not the case: W. virgo appeared as a result of a single “wrong” mating, judging by the number of accumulated mutations that occurred about 250 thousand years ago.

Also, W. virgo did not have any advantages over its parents in terms of physiological traits: this species did not stand out either in terms of resistance to heat and cold, or in terms of metabolic rate, or in terms of the number of eggs laid, the rate of development of offspring, and life expectancy. Nevertheless, for a quarter of a million years, W. virgo has successfully existed on the planet and even managed to spread throughout southern Australia, which its ancestors could not achieve.

It turns out that W. virgo has become a parthenogenetic species without any pluses and minuses for itself. But in this case, the question arises why the original species did not completely dissolve in each other, forming a single hybrid population. The scientists decided to test this by artificially crossing W. flavolineata and W. whitei and producing several hybrid females. None of them were able to produce viable offspring, which means that the unique mating that gave rise to W. virgo was also a very successful combination of circumstances, a kind of winning the genetic lottery, thanks to which the new species managed to hold out for so long .. A hybrid individual, obtained in the laboratory: unlike the “wild”, she laid only a few eggs that never hatched.

Further research into parthenogenetic species may allow us to answer questions about the benefits of not only bisexual mating, but avoiding it.

The results of the study are published in the journal Science.

Photo: A virgin grasshopper, or rather a virgin: this whole species consists only of females / ©findanexpert.unimelb.edu.au

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