Yellow eels are a common freshwater fish that are not only delicious food, but also the subject of scientific research. Because yellow eels have a peculiar physiological phenomenon: they can change from female to male, a phenomenon called sexual reversal. So, why do yellow eels undergo sexual reversal? How do they achieve gender transition? This article will unravel the mystery of the sex of yellow eels for you.
1. Life history of yellow eels
The yellow eel belongs to the family Zygopodidae and is a warm tropical freshwater fish. They are slender, scaleless, mucomotive, have a flat head, large mouth, small eyes, and lack pectoral and ventral fins. They like to burrow in the sediment and feed on shrimp, crabs, earthworms, insects, etc. Their lifespan is generally 5-6 years.
Yellow eels do not belong to one sex for life, as most vertebrates do, with females in the first half and males in the second half. This transition from female to male is called sexual reversal. In general, individuals with a body length of less than 22 cm are all females, and sexual reversal begins after laying eggs, and when the body length is 36-38 cm, the number of males and females is almost equal, and almost all males above 55 cm.
2. Sexual reversal mechanism of yellow eels
Sexual reversal in yellow eels is a complex physiological process involving the regulation of multiple factors. There is no fully clear explanation yet, but there are several possible causes:
- Genetic factors: The number of chromosomes in yellow eels is 2n = 48, of which there are two pairs of sex chromosomes (XX and XY). During embryonic development, the X chromosome is inactivated or missing for some reason, so that all individuals appear as females. As the age and environment change, some individuals reactivate or acquire X or Y chromosomes and thus transform into males.
- Environmental factors: Temperature and light are important environmental factors affecting the reversal of yellow eel. In general, the temperature is around 28 ° C, and the light is light for a long time, which can promote the transformation of yellow eels into males. At a temperature of about 22 ° C, in a dark environment for a long time, it can promote its transformation into a female.
- Hormonal factors: Hormones are important substances that regulate the reproductive development and function of animals. In yellow eels, two main hormones are involved in the reversal process: follicle-stimulating hormone (FSH) and mesenchymal cytotropin (LH). FSH mainly acts on follicular cells in the ovaries and promotes the development and maturation of oocytes; LH mainly acts on the mesenchymal cells in the seminal nest and promotes the development and maturation of spermatogonia. In the female stage, FSH levels are higher and LH levels are low; In the male stage, FSH levels are lower and LH levels are higher. In the inter-androgynous phase, FSH and LH levels are moderate.
Yellow eels are freshwater fish with a sexual reversal phenomenon, which can change from female to male, a phenomenon that may be related to genetic, environmental and hormonal factors. The sexual reversal of yellow eels provides us with an interesting model for studying the sexual differentiation and regulation of animals, and also shows us the wonder and diversity of nature.
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