Oysters can be hermaphrodites? These creatures are performing a special "survival of the fittest"

In Farewell My Concubine, the young protagonist Xiao Douzi has a classic line: "I am a girl, not a man."

The ambiguous gender transformation in the subconscious helps the protagonist to broaden his acting style to some extent, but it is also an important reason that ultimately leads to tragedy.

For humans, gender is a "role setting" that comes with birth. The chromosomes received at fertilization determine whether each newborn is a boy or a girl. If humans want to change their sex, they need to undergo complex surgery to achieve it.

But in the vast natural world, many animals are born with the ability to "change sex", some of which are influenced by the environment, while others do so for the purpose of reproduction.

Oyster

Most oysters are dioecious, but a few are hermaphroditic. Oysters change sex based on their environment.

Oysters have two sexual phases. When protein metabolism is active, the female phase is dominant; when carbohydrate metabolism is active, the male phase is dominant.

In fact, nutritional conditions are not the only factor that determines the sex of oysters. The phenomenon of male proto-maturity of oysters is the determining factor that causes their sex change.

Image source: hippopx

Many oysters are male when young, but they have both male and female gonads and can switch back and forth between male and female. Usually, sperm is formed before eggs, so when they first mature, most oysters are male, and the sex is determined by nutritional conditions in the second year.

The better the nutritional conditions, the more vigorous the growth of oogonia in the body, and the higher the ratio of female oysters will be. Conversely, the higher the ratio of male oysters will be.

Conger eel

The moray eel is a hermaphroditic animal that can change sex at any time and in any place. The sex change of the moray eel is determined by the environment in which it lives.

When the environment in which they live is limited and there is insufficient food, or when the density of similar species is high and the competitive pressure is high, the conger eel will turn into a male to increase its strength and plunder food.

Image source: hippopx

When food is plentiful or the surrounding environment is not harsh, the moray eel will turn into a female. Taking advantage of the environment can be considered as the wisdom of moray eels in survival.

Grouper

Groupers are considered "sex change experts" in nature, and they usually change their sex at dusk. Unlike other creatures that can only change their sex once in their lifetime, groupers can change their sex multiple times a day.

This sex change often occurs when two groupers mate, with one becoming the female first and the other the male. After mating, they swap genders and roles and reproduce again.

Image source: hippopx

In the opinion of scientists, this magical phenomenon is mostly due to the fact that the eggs of grouper are too large. If only females are allowed to lay eggs, it will consume too much of their physical strength and life. If both males and females are responsible for the tasks of ejaculation and ovulation, it will not only reduce the pressure on females, but also be more conducive to the reproduction of organisms.

Clownfish

In nature, males generally have more advantages in strength, but in the process of sex change, not all creatures change from female to male. Clownfish is a typical "negative representative".

In the sea, clownfish and sea anemones live in close symbiosis. One sea anemone can usually only accommodate two clownfish. Due to space limitations, these two clownfish can only "love each other until they are old."

Image source: Wikipedia

In terms of reproduction, the number of offspring that clownfish can produce has nothing to do with the number of sperm in the male fish, but depends on the number of eggs laid by the female fish. Therefore, when the female fish has an absolute size advantage, it is most beneficial to reproduction.

In this case, it would be a better strategy for the clownfish to develop into a male when it is smaller and then change into a female when it is fully developed.

In addition to their own factors, the gender change of clownfish is also affected by the real environment: when male fish lose their mates, they will change their gender, and then find a male fish smaller than themselves to mate, and then lay eggs by themselves. Through gender change, a new family is established.

Frogs

In addition to spontaneous changes, frogs' degeneration is more often caused by changes in their living environment.

Image source: hippopx

Researchers accidentally observed that African clawed frogs can change their sex freely in the laboratory. Then, researchers found that more and more male frogs turned into female frogs outdoors. Along with the change of sex, the reproductive organ function of African clawed frogs was also fully transformed, but this was not a normal natural process. The culprit of this change was a herbicide called "atrazine".

This herbicide is strictly prohibited in many places. Once it enters the river basin, it will destroy the sexual development of frogs, inhibit the production of male hormones in frogs and promote the increase of female hormones.

The arrival of this herbicide has brought a devastating disaster to frogs, following the impacts of climate change, habitat loss and invasive species.

The transformation in nature is simple and direct, and perhaps this is the ultimate meaning of "casualness". No matter how many times it changes, it is to find a way of survival that suits oneself and the race in a fierce environment.

END

Reviewer: Ran Hao, a well-known popular science writer.

Tadpole Musical Notation original article

Editor/Xiao Xitushuo