Evolution of sexual habits

American scientists who studied ticks found that these primitive arthropods, over millions of years of evolution, managed to change the type of sexual behavior at least twice. One of the species of the superfamily of crotonioid mites once abandoned sexual reproduction in favor of parthenogenesis, but then, for an unknown reason, decided to return to an active sexual life. This amazing conclusion, as reported by the New Scientist magazine website, was made by a group of biologists from the State University of New York (Syracuse) led by Roy Norton.

Asexual reproduction among numerous families of ticks is not uncommon. Many species prefer procreation without the participation of males, using the mechanism of parthenogenesis. In this case, females lay eggs containing an exact copy of the mother's genome. Accordingly, the hatched offspring inherits all the characteristics of its parent. However, the mites, having refused to use males and excluded any hints of sex from their lives, for some reason did not remove the genes of the stronger sex from their DNA. Sometimes, for some reason, same-sex ticks give birth to males - however, they are sterile and do not participate in the reproduction process.

Norton's group calculated the pedigree of various species of mites, both asexual and those that retained the sexual method of procreation. When constructing a family tree, it turned out that at least one species of the Crotonioidea family was never able to completely give up sex. At first, these mites, like some of their relatives, completely switched to parthenogenesis, but then, after millions of years, males again began to participate in reproduction.

Biologists suggest that such unusual changes in the life of ticks could be caused by external conditions. “Crotonioids spend a lot of time in trees, where the environment is harsher than in the soil,” notes Roy Norton. Parthenogenesis is more effective in a situation where the species does not need to constantly adapt to new situations. And in the presence of unusual stimuli, ticks could again need the presence of individuals of two sexes. And then the “male” gene, which had been dormant for a long time, could be activated again - to increase the chances of survival of the species.

Vladimir DZAGUTO