Finding NemA?

October 11, 2010

Torah Kachur

How can you not love Marlin?  His heart-wrenching and hilarious quest to find his cherished only son...Nemo.  But what happens when his search ends in finding his son has magically transformed into a female clownfish.  It probably wouldn't be that funny.


        Torah Kachur Science in Seconds sex change reef fish clownfish nemo sequential hermaphroditism


The clownfish, and many other reef fish, can show a sequential hermaphroditism lifestyle.  In other words, they can naturally change sex in response to different conditions.  These conditions generally involve the number of males in the current school, or harem.  For example, the death of a male from a group of fish will stimulate the sex change of females into males.  The most common form of sex change in fish is protogyny - where a female can change into a male, which is a bit surprising because the most overwhelming sex change in humans is from male to female, Cher's daughter notwithstanding.


Admit it, you've wondered what you would do if, for only day, you could change sex.  What your body would feel like with a penis all of a sudden down there annoying you in jeans.  Or breasts that sprout on your chest and you can't seem to figure out how to tame them.  For fish like Nemo the sex change operation usually occurs over a few months. 


The massive changes that have to take place is incredible - anatomical and physiological changes have to accommodate all the differences between the sexes.  Including the undeniable higher IQ in females.  Our understanding of the driving forces for natural sex changes is slim - a few genes have been implicated like the H-Y antigen and a couple of hormones, but we really know nothing about this drastic transformation. 


What is maybe even more puzzling is why sequential hermaphroditism evolved, or, more importantly, why it isn't more common.  Changing sex in a lifetime is very evolutionarily favored because the most common driving force for natural sex change is to maintain a desirable proportion of males to females.  With the right ratio of males to females, the overall fitness of a species increases which should therefore eventually become a common trait.  But the fact that there are only a few lucky species that get to try it both ways is likely due to the incredible energy it takes to change sex and the length of time when they are changing sex and are removed from the fertile population....not to mention having to buy a whole new wardrobe.



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