Dominance Regulated Sex Determination

Aka, “Biology is Fricking Amazing”

My Evolution of Behavior class is full of amazing, insane facts about animals. Every day I leave that class excited to share these random facts with people, so you get some of them! While I could attempt to explain things in my own words using my notes from class, I’m going to be lazy and use Wikipedia. It probably has more information anyway.

From the Wikipedia entry on clownfish:

“Each group of fish consists of a breeding pair and 0-4 non-breeders. Within each group there is a size-based hierarchy: the female is largest, the breeding male is second largest, and the male non-breeders get progressively smaller as the hierarchy descends. If the female dies, the male changes sex, becomes the breeding female and the largest non-breeder becomes the breeding male. The fish apparently form lifetime pairs, exhibit courting behavior, and depending on the size of the female spawn about 400-1500 eggs per cycle. The expected tenure of breeding females is approximately 12 years and is relatively long for a fish of its size, but is characteristic of other reef fish.

It has been unclear why the non-breeders continue to associate with these groups. Unlike non-reproductives in some animal groups, they cannot obtain occasional breeding opportunities, because their gonads are non-functional. They cannot be regarded as helpers at the nest, since it has been found their presence does not increase the reproductive success of the breeders. Recent research (Buston, 2004) suggests that they are simply queuing for the territory occupied by the breeders, i.e. the anemone; non-breeders living in association with breeders have a better chance of eventually securing a territory than a non-resident. The probability of a fish ascending in rank in this queue is equal to that of the individual outliving at least one of its dominants because an individual will ascend in rank if any one of its dominants dies, and not simply when its immediate dominant dies.”

Or as my professor said, “What they didn’t tell you about Finding Nemo was that at the end, Nemo turns into a girl.”

Wholesome Disney movie, or insidious plot to introduce transsexualism to our children? You decide.


  1. Azwildgreen says

    I don’t see Disney including or even acknowledging transsexuals in any of their works any time soon. To be fair, this may not be a matter of them supporting rigid hetero sexuality and suppressing any other interpretations, and more a matter of their target audience thinking that cooties are the number one health problem in America. I spend most of 2009 working a phenomenal internship at Walt Disney World, and they had no problems listing LGBT support groups along with the other programs they were in contact with for their employees sakes. Likewise, if you want to see a possible/probable human transgender “Disney” character, I would point out that the Disney/Sqare Enix owned character Xion from the videogame Kingdom Hearts has a (ahem) complicated background, complete with very real lingering doubt about her/his physical sex and orientation. A minor character, to be sure, and they didn’t really explore the issue, but small steps will still take us somewhere.

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