Introduction to sex reversal

In fact, the transsexual behavior such as "hen becomes rooster" is not just a patent for chickens.

In nature, the phenomenon that functional male or female individuals become functional heterosexual individuals is called "gender inversion". Sex reversal only occurs at the sex level of gonads and the resulting changes in phenotypic characteristics, and does not involve chromosome sex. Mammalian germ cells can only develop in the direction of sex determined by sex chromosomes, so no functional sex reversal has been found in mammals so far. However, in fish, amphibians, etc. , functional inversion can occur. There are many factors that cause sex reversal, such as animal's physiological state, external environment and hormone treatment. Some fish, such as Monopterus albus, can be hermaphroditic and spontaneously inverted under normal circumstances. Androgynous individuals have two types of sex organs, and their development can be carried out alternately, that is, "male first, female second" or "female first, male second".

Environmental factors can also induce reversal. Removing males from a group of fish can make some females become males and produce normal sperm. The embryo of the maned lizard living in the Australian desert can change sex from male to female in high temperature environment.

Monopterus albus is female from embryonic stage to first sexual maturity, and its gonad is ovary. After laying eggs, the ovary gradually becomes the testis and becomes a male individual. However, although the transgender mane lizard has female organs, it is still genetically male.

It is easier for hens to crow than for the rooster lay eggs.

The news that a hen becomes a rooster is often heard, but under natural conditions, the situation that a rooster becomes a hen is much less.

This is because only female birds have asymmetric reproductive system development. The gonads of bird embryos come from the genital ridge, and the reproductive ducts come from the Mullerian duct and the Wolff duct. In females, the left gonad and Mullerian duct developed into functional ovaries and fallopian tubes, while the right side remained primitive and evolved to maintain weight and facilitate flight. In males, gonads and Wolff's ducts developed into symmetrical bilateral reproductive systems, while Mullerian ducts degenerated.

Although the sex of birds is initially determined by sex chromosomes, sex differentiation is controlled by sex hormones in the incubation stage. Under normal circumstances, the female gonads of ZW embryos develop first, secrete hormones, promote the development of female characteristics, and inhibit the development of male gonads. ZZ embryos are the opposite. Therefore, if chicken embryos are treated with estrogen at the initial stage of incubation, it can lead to different degrees of female development of male embryos.

In some areas, there is a saying that "when hens crow, there is misfortune at home", so if you want to be Mulan, you have to risk being slaughtered. ...

Because adult hens only have the left ovarian fallopian tube to develop, once they are damaged by external stimuli, they can no longer produce enough hormones. At this time, the undifferentiated primordia of the reproductive system on the right side are no longer inhibited by hormones, and then develop into testicles, and hens become fertile cocks, resulting in the situation of "treating chickens for the morning".

In fact, anyone who has lived in the countryside may realize that it is much easier for a hen to become a man than a rooster to become charming.