If you have ever seen the movie Finding Nemo then you may feel like an expert in clownfish. One thing the movie didn’t show was what actually happens when the mother clownfish dies. While you could argue that Nemo’s dad became a maternal figure in the movie, in reality, the father clownfish would literally change sex and become female. We are not sure why this strange behavior was not included in the movie, probably because it would cause too many questions for parents when children returned home from the cinema. Don’t worry, we are here to answer your questions.
Clownfish are unique in that they live in schools of fish with one specific rule. There is only one female and all the others are male. The female of the group is usually the largest of the fish and is in charge. There is then one man who is her mate who is the second-largest and all the others rank below them. The largest male will take most of the food so that the other fish can never grow too big and take over from him.
His role is to be the only fish in the group that breeds with the female. The female fish will lay her eggs and he will fertilize them. The male will then look after the eggs for a while until they are ready to hatch. Once hatched the job of parenting is over. The baby fish (like Nemo) will swim to the surface of the water and feed on plankton until they grow larger. It appears then that Nemo really wasn’t so different from every other clownfish.
If the female dies then the male clownfish will eat without restriction. He will continue to put on weight and become the female of the group. From there the cycle simply repeats itself. This new female will choose the largest male of the group who will become the new top male. It all sounds like a terrible reality TV show in the making, but it is true.
While it is a strange change that naturally takes place, the question is why. Scientists believe that this change happens because of the lack of options in the clownfish world. The clownfish (unlike Nemo) does not stray far from home and this means there are very few females in the surrounding area. If a male was not able to change to be a female then there would be no opportunity to mate and the ability to reproduce would be threatened. While it is one of the strangest forms of survival behavior it is an incredible insight into the natural world.