It would seem that the sex of any animal is determined at birth and remains unchanged (unless, of course, we are talking about gender reassignment operations, which, due to dissatisfaction with life, some representatives of humanity resort to). Scientists have counted over 500 species of fish that can naturally change their sex in adulthood in response to environmental changes.
As a model for studying this unique phenomenon, scientists took the fish "blue-headed thalasoma" (Thalassoma bifasciatum). This species of aquatic vertebrate animal lives in the Caribbean. The considered maxillary can be found on coral reefs. Here they live in groups. The male dominates - gender is clearly visible by color - blue head.
Females have beautiful yellow scales. Not only women are hard without men: if the male is far away and the “ladies” are alone for a long time, the largest of the females in just a few days turns into a male. At the same time, her behavior changes in a matter of minutes, color - in hours. But, in addition to external signs and character, physiological indicators also change: her ovary turns into a testicle. Already on the tenth day, the ex-female begins to produce sperm.
Scientists in their study used innovative genetic approaches - epigenetic analysis and RNA sequencing. This allowed them to establish exactlyat which point in time certain genes turn on and off in the fish. This study allows us to understand how genes can change during the development of all animals (including you and me). Understand how external factors, nature, and the environment influence this process.
As a result of the study, it was found that gender change occurs due to complete genetic rearrangement of the gonad. At first, the genes responsible for the existence and maintenance of the normal state of the ovary are turned off, then the genes responsible for the development of the male principle are activated.
To assess the completeness of the picture, in addition to Thalassoma bifasciatum, scientists studied another family of fish - Aranian. They have a similar mechanism for changing sex, which allowed scientists to draw conclusions about the presence of an ancient gene control system under the influence of external circumstances.
