Sometimes male, sometimes female? It turns out these fish can change sex!

Did you know that changing sex is quite common in the fish world?

Fish changing their gender is one of the most bizarre phenomena in nature. Different fish change their gender at different times, but the reasons for changing their gender are generally the same - to adapt to survival and to reproduce more advantageously. And fish do not change their gender through surgery!

Yellow eel - first a mother and then a father

Generally speaking, female fish have ovaries in their bodies and male fish have testes in their bodies, and they do not change from birth to death, but eels are different.

Newly hatched yellow eels are all "female" with ovaries, which can be called a "country of women". But when the yellow eels mature and fulfill their responsibility as a mother - giving birth to yellow eels, their physical characteristics begin to change.

The tissue that originally grew egg cells gradually transformed into a testis that grew sperm, so the female eel suddenly changed into a male eel that can release sperm. At this point, it is fixed as a male, and it will not change back to a "female body" even after releasing sperm.

It can be said that the eel is a mother first and then a father in its life. This yin-yang transformation process of the eel is called "sex reversal" in biology. This characteristic is very beneficial to the eel species. Every year, a group of female eels will become male eels, and every year another group of female eels will reproduce, and this cycle will maintain the continuity of its species.

Conclusion : After giving birth to baby yellow eels, the yellow eel mother becomes the yellow eel father.

Bluehead fish: sex is determined by size

The bluehead croaker, which lives on coral reefs in the western and central Atlantic, has brightly colored males and drab females, but the drab females prefer to mate with only the largest, most colorful males.

Therefore, the largest male fish has the greatest advantage during the peak of the reproductive season and can mate with female fish more than 40 times a day. Therefore, when the bluehead fish is still small, it always behaves as a female and begins to lay eggs during the reproductive period. Once it grows large enough, it will transform from a female fish to a male fish and begin to perform male functions.

The gender change of bluehead fish is not only limited by physical factors, but also influenced by the social environment. If the largest male fish on the coral reef is removed, a large female fish will change gender in just a few days and turn into a brightly colored male fish, replacing the previous male fish.

Conclusion : When the bluehead carp grows big enough, it transforms from a female to a male.

Red Snapper: Gender Change for the Family

Red snappers live in a family in the ocean. There is only one male red snapper in this family, and the other twenty or so red snappers are all female. This one male red snapper leads the entire family, responsible for the safety of the family and the reproduction of its offspring. If this one male red snapper dies, the female fish will be at a loss and panic.

But before long, the slightly larger female fish in the family group will become a male red snapper and lead the family to start a new life. Someone has done an experiment and found that if male and female red snappers are separated by glass so that they can see each other, their characteristics will not change.

But if the glass is replaced with a wooden board, the female red snapper will change its gender soon, just like the male red snapper lost.

The reason why red snappers change from female to male is that male red snappers have bright colors on their bodies, which send out special signals underwater.

Female fish are very sensitive to this kind of color. Once the light color of the male fish disappears, the strongest nervous system of the female fish is affected first. Then a large amount of male hormones are secreted in its body, causing the ovaries to disappear, the testicles to grow, and the fins to become larger. In this way, a male fish is "born".

Conclusion : The red snapper's sex change was completely out of helplessness, as a family cannot be without a leader.

Clownfish: Double pressure from environment and reproduction

Of course, not all sex changes are from female to male, and the clownfish living on the coral reefs of the Indian Ocean are an exception.

Clownfish live closely with sea anemones. Since the size of anemones can usually only accommodate two clownfish, this space limitation forces clownfish to practice a monogamous pairing system.

In addition, the reproductive success of a pair of clownfish is mainly determined by the number of eggs laid by the female, not the sperm production of the male. Therefore, it is only in the best interests of both sexes when the largest individual is a female. In this case, the best strategy is for the clownfish to behave as males when they are small and then transform into females when they grow up.

According to research, the gender transformation of clownfish is also controlled by the social environment: if the female fish is taken away, the male fish that has lost its mate will combine with a male fish that is smaller than it, and then change its gender, turn into a female and start laying eggs. In this way, through gender transformation, a new family is established.

Conclusion : For clownfish that practice monogamy, sex change is inevitable due to living space and fertility pressure.

Blue-striped grouper: Change whenever and wherever you want

Blue groupers living off the coast of Florida and Brazil can change sex several times a day. Every evening, male and female blue groupers undergo sex changes, and this may happen several times.

If two fish mate and lay eggs, one of them will be the female first and the other will be the male. Once they have finished mating, they will switch genders and reproduce again. This phenomenon is called sex change, also known as "hermaphroditism" and "cross-fertilization".

Scientists analyzed that it might be because fish eggs are much larger than sperm, and if only females were allowed to lay eggs, the burden would be too heavy and the cost would be too high. If both parties were responsible for both sperm and ovulation, the chances of reproducing offspring would be greater.

Conclusion : Bluestriped grouper is a very “adaptable” fish.

In addition to the above, they are also fickle

Oyster

Oysters are also both male and female. Interestingly, the gender of oysters changes from year to year. Last year they were male, this year they become female, and next year they become male again. The time of change is different for each oyster, and it does not happen at the same time.

Sea slug

For sea slugs, the above sex change methods are too slow. We can never be sure whether the sea slugs living inside are male or female. Their gender depends entirely on the gender of the other party. If the other party is male, it will become female; if the other party is female, it will become male.

It is still a mystery why lower marine animals undergo sex change. But in any case, this is also a unique function that some lower animals have evolved in the process of evolution in order to adapt to survival and reproduce offspring more advantageously.