 |
(Photo: VNN) |
In the animal kingdom, eels are a unique species capable of changing sex: female eels can transform into males. Generally, larger eels do not carry eggs, while smaller ones do. But why is that?
Most fish possess either ovaries or testes throughout their lives, and their sex remains unchanged from birth to death. However, eels are different. When eels are born, all individuals have ovaries, meaning they are all female. As young eels mature and start to lay eggs, the tissue in their ovaries gradually transforms, changing the cells that produce eggs into testes that produce sperm. Consequently, female eels become male eels capable of releasing sperm.
This characteristic of eels is referred to by scientists as “sex reversal.” After a female eel spawns once, her ovaries transform into testes, permanently changing her from female to male, and she will no longer lay eggs. For an entire population, each year, a group of female eels will spawn, leading to the formation of a population of male eels, thus ensuring the continuity of the species.
