Animals who change sex or reverse sex roles And Why do some species change sex?

in #nature8 years ago

If animals were on Facebook, they'd be pretty stoked about the non-binary sex options out there. 

Humans have spent the last few millennia attempting to paint biological sex as purely black and white, and only in the last few years has that dichotomy slowly blossomed into more of a continuum. The natural world, however, doesn't have those sticking points. Instead, nature produced so much variation in animals and insects, that it would be ridiculous to even suggest that there are only two sexes out there, or that they can only be one. For example, some animals are born intersex, just like some humans are. That means they possess both categories of male and female sexual characteristics, primarily judged by the appearance of testicles and ovaries, also known as gonads. Gonads are just any organ that produces gametes, which are necessary for reproduction. 

Some lower animals, such as earthworms or snails, are inherently intersex, which in this case is also called "simultaneous hermaphroditism" this means they have both ovaries and testes. When they mate they pass packets of sperm back and forth before putting the fertilized cells in a cocoon. Some animals are born with one sex, and for a variety of reasons undergo, what is basically a self-induced sex change. This is called "sequential hermaphroditism". A number of fish, amphibians, and reptiles are famous for this ability, and in some cases, they'll change sex just based on social hierarchy. 

The clownfish, for example, is structured in a social hierarchy with the only female fish at the top. If this top female clownfish dies, then the most dominant male takes her place, and in doing so, changes its sex to female. The same thing happens with wrasses, but in reverse, with a school of females and a male at the top. There are also animals that are considered one sex but show characteristics of another. 

In one African game reserve, keepers discovered a group of female lionesses sporting thick masculine manes, and producing loud guttural roars, which these lionesses used to trick predators and even safari guests into thinking they were male lions. According to one biologist interviewed in Popular Science, these lionesses likely have an overabundance of testosterone. This is similar to the increase experienced by older women after menopause . Kind of like these lionesses, many older women begin to display some secondary sexual characteristics which we more associate with men, like hair growth and a deeper voice. 

Biological sex is a wide spectrum, with plenty of overlap, loopholes, shortcuts, and just plain unexplainable weirdness; at least that's how it looks to humans. But, if everyone else is comfortable with their sex, maybe we're the ones with the weird obsession? 


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Taking hormones I discovered that people really do get thrown off if they can't tell the sex of a person. I've been perceived as a very feminine to a very masculine person, and it was in between that I experienced most violence. When people would see me out in the streets they would actually stop their vehicle, roll down the window to ask what my sex was. Some wouldn't even stop, they'd just slow down and yell their question as I was walking. Why would they feel like they needed to know if they were never going to see me again? I always thought it was weird how it could affect some people to not be able to categorize something. Like some of those people could have hurt themselves looking away from the road while driving...

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