The Real Nemo Would Have Become His Own Mom

Here is a fact that will make you rethink everything you thought you knew about a beloved animated fish movie. In the wild, all clownfish start life as males. Every single one. The female of any group is the dominant fish, and when she disappears, nature steps in with a plot twist that screenwriters never saw coming.

Clownfish live in small social groups within a single sea anemone. The largest and most dominant fish is always female. The second largest is the breeding male. When the female dies, the breeding male physically changes sex — growing larger, adjusting its hormones, and becoming fully female — ready to take her place as the new matriarch of the anemone. The remaining males shift up in rank accordingly, and life in the anemone carries on.

This means the plot of Finding Nemo contains a spectacular biological irony. When Nemo's mother is killed at the beginning of the film, Marlin — as the dominant remaining male — should biologically have transformed into a female and become Nemo's new mom. Instead, he went on an entire ocean adventure while completely ignoring what his own species' biology was trying to tell him. We can only assume he was too emotionally overwhelmed to notice.

Scientists call this sequential hermaphroditism, and clownfish aren't the only ones doing it — wrasse, parrotfish, and several other species pull the same trick. Nature, it turns out, is a lot more flexible about these things than Hollywood tends to be. Just something to think about next time you rewatch the film.