Sunday, February 23, 2014

Clownfish: Twisted and Confused

"Clownfish and Anemone"

One of America’s most famous and adored marine fish, the Clownfish, may be even goofier than their name suggests.  These cute orange and white fish that we have grown to love, thanks to the Disney movie “Finding Nemo”, actually live a very twisted sexual life.  You see, the clownfish is hermaphroditic, meaning that they can play the role of both male and female fish.  Although this seems very strange to us humans, it is actually a fairly common practice in the aquatic world. There are said to be as many as 21 families of fish that behave in this kinky manner (Stephens). I don’t know about you but that makes me think twice about the cleanliness of the ocean we swim in.

The clownfish specifically is known as a protandrous sequential hermaphrodite, not to be confused with the protogynous sequential hermaphrodites.  To break this down, sequential hermaphrodites are those which “develop as one gender before changing to the other gender” later in life (Cooney).  Of the sequential hermaphrodites there are the two types.  The protandrous start out as males and can later switch to females, while the protogynous develop as females first and then switch to males.  So let’s tie this all together in terms of the clownfish. 

Imagine you are a clownfish that just hatched from its egg.  You start off life as an undifferentiated male with just your mom and dad around.  Sadly, something happens to the mother and she’s gone which just leaves you and your dad living in this small hypothetical population.  In the name of procreation your dad changes into a female to allow for spawning.  As if it isn’t weird enough, you now must breed with your female father to start a new generation.  This happens and a new generation of undifferentiated males is hatched.  Tragically, after the spawning season is over a shark swam in and ate the father! Being the oldest male you take a long look around and find that there aren’t any clownfish ladies swimming around and thus it becomes your turn to become a female.  This is the reproductive behaviors of the clown fish and in general for any sequential hermaphrodite (Cooney). 
Image from Cooney

Although this seems very strange to us humans who don’t naturally change genders, it is both commonplace and beneficial for these fish.   For a small clownfish, it is a truly a “fish-eat-fish” ocean out there.  Living this type of hermaphroditic lifestyle ensures that there are always both male and females around to safeguard the population density.  

If you are still baffled by how these fish reproduce (don't worry its so foreign to us that it is not an easy concept to grasp) then check out the short video below. It does a great job at displaying how the clownfish changes sex and reproduce. 

BeckmanInstitute. “Sex-Changing Clownfish.” Online video clip. YouTube. YouTube, 27 September 2012. Web. 23 February 2014.

Chow, Samuel. Clownfish and Anemone. 7 October 2010. Ask Nature. Web. 23 February 2014.

Cooney, Patrick. “Finding Nemo Lied…” The Fisheries Blog.” The Fisheries Web. 18 February 2014.

Stephens, Christina. “List of Hermaphrodite Animals.” Animals. Demand Media. Web. 18 February 2014.


  1. Thanks for explaining the process of protanderous sequential hermaphrodism in a step by step example. It really made it easier to understand how the clownfish change sex. Now that I understand the process, why didn't Marlin change into a female when Coral died? Come on Disney.. get it right! :)

  2. Neat post! Thank you for sharing. I did not know that fish could have this sort of reproductive behavior. It seems like the only option though if you are one of only two of your kind left in a population.

  3. I think this would have made Finding Nemo really disturbing if Disney would have stuck with the facts! In all seriousness: I had no idea that the clownfish did this, and I think it's pretty neat. I would assume that once you change you can't go back, correct?

  4. Lets all be glad Disney did not make Finding Nemo accurate! I read that some fish species have the ability to switch back and forth between genders, but many can only switch once. I didn't find anything about the clownfish specifically switching mulitiple times, so I would assume it can only switch once.