Neat Trick of Clownfish (“Nemo”) : Changing Sex

By Shlomo Maital  


   Remember the animated movie, Finding Nemo, starring the clownfish (or anemone fish) Nemo, and his Dad? 

   Clownfish are indeed amazing – but for reasons different than those in the movie.  They can change sex, easily and quickly.  According to, anemone fish stay very close to the anemones that are their natural environment.  This limited mobility makes mating tough.  It’s like, every eligible girl is sort of your sister.   Nature has a solution, an amazing one.   Because clownfish are ‘hermaphrodites’.  And all are born male!

    When a male clownfish pairs with another male clownfish (all clownfish are born male), one of them will simply turn female so that the two can spawn. When the female dies, the largest male in the area will take her place by turning into a female. Then, one of the more dominant non-mating males will begin mating with her.

  With other hermaphrodite species, the sex-change process takes a long time, up to 30 percent of the lifetime of the creature.  But not for Nemo fish.  They do it very fast.  Male sex organs, gonads, literally change quickly into female ones.   Amazing how the random mutations of evolution create magic. 

   What if humans could learn the Nemo fish trick?   The possibilities are endless.