Tag Archives: hermaphrodites

It’s a question of… having sex like fish

Sometimes you learn the most incredible things in places you’d least expect. It happened to me the other day when I was visiting the Parisian aquarium (Cineaqua). I suppose the things I discovered are common knowledge to some, but to me it was big news.

It all started when my son got talking with a young woman working there. She showed him a fish and told him it was 22 years old. I started wondering if it was time to send our sole goldfish at home to “a farm” somewhere (seeing myself retired with it is not an appealing vision). Then she turned to me and asked if she could tell him about hermaphrodites. I promptly agreed. Having recently had to explain to my offspring what porn was, I didn’t mind leaving this one to her.

It turns out that 10% of fish are hermaphrodites. I had no idea. This particular one – a grouper of some sort – started life as a “non-sexual” fish, then became a female at 4 years old and a male at around 12. As the lady told my son: “when it gets really fat, you know it’s turned to a male”.

Needless to say, I spent a few hours looking up the sexual lives of fish afterwards. That’s how I now know about protandrous hermaphrodites (fish that first develop to males, then to females) and protogynous hermaphrodites (the opposite, like the grouper). I also found out that many sequential hermaphrodites (that’s the general term for fish capable of transforming from one sex to another) use their abilities to maintain the balance between male and female fish populations.

For example, in a monoandric harem (ok, I’ll stop using words I didn’t know existed a few days ago) – a harem consisting in one male and several females – if the male dies for some reason, the strongest female will “turn” (within days!) and take his place. A sex change to make up for lack of males in one place? Fish are genius!

As for reproduction, well they’re quite progressive too, being avid partisans of random in-aqua fertilization and group sex. As the aquarium woman told my son: “They all get together and just spurt out sperm and eggs in the water and it all mixes and ends up making baby fish” (and yes, I was forced to have the sperm and egg conversation later on…).

It turns out that sharks are some of the only fish to actually copulate. They are also one of the only species to have different and external “genitals” so you can tell male and females apart (though sharks don’t have actual penises).

Of course, not all fish swim around “spurting” their reproductive material. Some females make nests, lay eggs and wait for a male to come along and “sprinkle” them. Sometimes, the male makes the nest (a fancy bubble nest), he then gets a female in there and “wraps” around her, squeezing her till eggs drop out. Others are “live bearers” (like guppies) and carry their eggs internally. And wait till you hear this: the female guppy can “stock up” on sperm and use it at different times, so she doesn’t have to wait for a male to be around to spawn. Again: genius! (True, these same fish have a tendency to eat their newborn progeny too, but hey, nobody’s perfect.)

And last, but not least, let’s not forget the female fish that take a big mouthful of eggs and sperm and store them in their mouths till the eggs hatch (note to men: see, fish don’t swallow either).

While I may not envy fish for their sex lives (though the water element is pretty enticing and the sex change possibilities interesting), I’m truly enthralled by having found out about yet another brilliant way nature works. And I now look at our goldfish with renewed interest…


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