If you think that living without sex is not possible and that no animal as a species can survive without sexual reproduction, you should know about bdelloid rotifers, a microscopic animal that lives in freshwater and measures between 0.150 and 0. , 7 mm. To the amazement of scientists, the organism managed to survive for 50 million years without sexual reproduction. So much so that the animal’s avoidance of sexual reproduction made scientists believe that microscopic animals were never capable of sexual reproduction. But this is not the truth. Recent studies show that older bdelloids have already had sex.
To better understand this, when scientists chose a particular species of bdelloids – Adineta vaga, and tried to sexually reproduce them, they were shocked to find that the animal had lost its sexuality. During the researcher’s experiment, the sex cells of A. vaga could not cross each other – mix the DNAs of both parents by swapping portions, a key step in cell division and the scientists concluded that A. vaga could no longer reproduce sexually. The reason the sex cells did not cross is that by evolving separately through asexual reproduction, the DNAs of the chromosomes of the organisms had become so different that they could no longer combine.
The loss of sexual reproduction could be considered bad news for bdelloids if scientists weren’t amazed at their evolutionary success. Sexual reproduction is considered evolutionarily beneficial because it combines DNA from both parents, which in turn provides genetic diversity. Diversity means less accumulation of harmful mutations and more genetic variation, which can provide a larger pool of organisms for natural selection to do its job. Genetic variation could result in more candidates capable of surviving environmental changes and thus advancing the species.
Asexual reproduction, on the other hand, does not provide genetic variation. This means that if a disease affects only one member of the population, it is likely that it will affect everyone since everyone has the same gene. In summary, asexually reproducing species would not be successful in terms of evolution. This is where bdelloids surprise scientists. The difference in their genetic material also revealed unexpected genetic variations. Although they reproduce asexually, they have been able to maintain and thrive in their genetic diversity. When scientists sequenced the genome – the complete set of genes – of A. vaga, they realized that the microscopic animal was unusually mixing its genes to achieve a variation similar to that of the crossbreed. Additionally, the animal is a notorious gene thief that steals genes from bacteria, fungi and even plants. Stolen items represent eight percent of the animal’s genes. Bdelloids can go another 40 million years without sex, scientists believe.