Asexual reproduction is often considered an evolutionary dead end.
Indeed, this mode of reproduction is supposed to lead over generations to an accumulation of harmful mutations (i.e., creating a disadvantage for the organisms that carry them), which inevitably leads to the extinction of the species.
For this reason, researchers have long been interested in the Bdelloida, microscopic animals with a strictly asexual reproductive mode.
Analysis of the genome of the bdelloid has shown that it is incapable of sexual reproduction. Indeed, this implies that the homologous chromosomes, coming from both parents, carry genes in the same order.
However, the researchers discovered that the genes of this animal do exist in two copies, but different order, and sometimes even on a single chromosome: there is, therefore, no homologous chromosome, as in the animal species sequenced until now. Such an organization does not allow the formation of gametes. And without gametes, there is no sexual reproduction.
Asexual Bdelloid: Reproduction
The bdelloid rotifers are found in abundance all over the globe (mainly in wetlands). After complete drying out or exposure to huge doses of radiation, they are able to repair their DNA and then resume normal metabolic activity. Moreover, biological and paleontological data suggest that they have reproduced exclusively asexually for tens of millions of years, an “evolutionary scandal” that runs counter to popular belief but is demonstrated by the authors of this study. Boris Hespeels, University of Namur.
In addition, the analysis revealed abundant traces of gene conversions, a kind of genetic “copy-paste” in which a copy of one or more genes is reproduced on another copy elsewhere in the genome by replacing it. The authors of the study published in the journal Nature, who belong to an international consortium co-led by CEA-Genoscope and the University of Namur, argue that this mechanism could greatly reduce or even completely eliminate the accumulation of harmful mutations.
Asexuality Reproduction Study:
This study would not only close the debate on the alleged asexuality of the bdelloid rotifers. Perhaps most importantly, it suggests that scientists can now determine whether a species is sexed or not by analyzing the structure of its genome. If the bdelloid rotifers have been able to survive without sexual reproduction for millions of years, it is likely that they are not the only animals in this situation.
Thus, this study challenges the commonly accepted idea that sexual reproduction is essential for animal species to perpetuate themselves. It also shows that asexuality is also a viable long-term evolutionary strategy for some animal species.