Anyone who tries to argue that changing your gender or sex isn't "natural" has clearly never spent time in the ocean. For many types of fish, a sex change is just a regular part of life. Let's look at seven sea animals that can change sexes like it's no big deal.
All clownfish (also known as clown anemonefish) are born male. Clownfish live in communities that consist of a dominant female, a dominant male and many sexually immature males. If the dominant female dies, one of the immature males will turn into a female to take her place.
Clownfish may have developed this ability because they rarely stray far from the stationary anemones that they have a symbiotic relationship with. If a group's dominant female dies, they cannot expect another female to wander into their anemone. So instead, a male member of the group must replace her.
Many species of wrasse can change their sex from female to male. Wrasse can be born male or female, but females may change if triggered by environmental cues. For example, female saddleback wrasse may become male if there are not enough males in the group.
Bluehead wrasse live in groups where there is always a dominant male protecting his harem of females. If the dominant male dies, the largest female in the group will change into a male to take his place.
Hawkfish are all born female, and they can change into males when they need to. But they also have the ability to change from males back to females.
Like bluehead wrasse, hawkfish live in groups that consist of one dominant male and a harem of females. If the harem gets too big, one of the largest females will change into a male and take over half of the harem. However, if a male harem leader was challenged by a larger male, he might opt to turn back into a female and allow the larger male to take over, rather than waste energy on a fight.
By changing back into a female instead of fighting a battle it would likely lose, the hawkfish maximizes its potential to reproduce.
4. Mushroom Coral
Not only can many species of coral reef fish change their sex, corals themselves can undergo sex changes. Some species of coral have both male and female gonads simultaneously, but mushroom coral is one species that can only be one sex at a time. Mushroom corals have the ability to change from male to female and then back again.
Scientists are not certain why this happens, but they think it may be a way to conserve energy. Producing sperm takes less energy than producing eggs, so if you are a coral, it makes more sense to be male when you are small, or when you are in some kind of distress.
5. Ribbon Eels
All ribbon eels undergo a sex change. They all start out life as males, as then transition to female when they reach a certain size (about 33 inches long). Ribbon eels also change colors when they change sexes. Males have a blue body with bright yellow jaws. When they transform into females, they become all yellow or greenish yellow.
6. Sea Snails
Multiple species of sea snails can change from male to female. The change usually happens when the male snails grow to a certain size, because larger snails will be more successful at carrying eggs.
A few years ago, scientists discovered that slipper snails change sex in response to physical contact with other slipper snails. The reason why physical contact triggers the change is still unclear.
7. Starlet Cushion Stars
Starlet cushion stars are a type of starfish that look like tiny cushions. All cushion stars are born male, but when their arms reach a certain length — between 9 and 16 millimeters — they become female. The reason for this change may be the same reason the mushroom corals and sea snails change sexes: Bigger animals make better moms.