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A strange Finding Nemo story. Clownfish males become females if their “wives” die

Clownfish, popular and beloved due to the Finding Nemo series, are odd little fish as biologists found that males change sex completely if their female mate is eaten or dies.

Marine biologists found that the popular and beloved clownfish have particularly odd feature. According to a research presented at the University of Exeter male clownfish, which are a distinctive orange colour with blue-white stripes bordered by black, become female to protect their anemone territory and their anemone fish group.

Clownfish, or anemonefish, live in tropical climates on anemones where they stay their entire lives. While the male fish tend to look after the eggs and fan them, the females take the role of protecting the territory by acting just like security guards, scanning the surroundings for predators, issuing warning calls and even launching attacks. And sometimes, the females have even been spotted attacking sharks.


Dr Suzanne Mills, an evolutionary biologist from École Pratique des Hautes Études at CRIOBE in France and Dr Ricardo Beldade, a marine biologist with Centre National de la Recherche Scientifique at CRIOBE, have researched the behavioural, physiological and hormonal changes in anemonefish, or clownfish, over several years in Moorea, French Polynesia. What she found was that when their female partners day, the males change not only their behavior but also become able of laying eggs and mating with younger males, in order to ensure the survival of the species.

And this makes for a completely new scenario for Finding Nemo. While in the movie, the little clownfish, after numerous adventures, is reunited with his father, in reality, he actually meats his mother.

“Anemone fish don’t move from their anemone for the whole of their life. The largest individual is the female, and if that female gets predated upon or dies, the male – Nemo’s dad – then changes sex and becomes a reproductive female. So when Nemo finally gets back to his anemone at the end of the film, he’s actually meeting his Mum,” Dr Mills told marine biologists at Exeter University.

The males change sex completely and now scientists are concentrating on investigating how these hormonal, behavioural and physiological characteristics of anemonefish are affected by climate change and other human-induced changes such as boat engine noise.

Sylvia Jacob