Finding Nemo (Another) Therapist

by | Aug 28, 2025 | The STEMM Collection

What could possibly be worse than a father eating his son because he’s deformed? Well, you’re about to find out. This is part two of finding Nemo a therapist (yes, Disney’s Finding Nemo). Why? Because clownfish are slightly traumatising. Click here for part one if you don’t believe me (and for some nontraumatising background on clownfish).


Now for more reasons Nemo needs a therapist:

Marlin and Nemo must have been in the Clownfish Olympics

Clownfish can barely swim between anemones, let alone from the Great Barrier Reef to 42 Wallaby Way, Sydney. What were those guys eating?

 

Marlin has a weird obsession with Nemo

Parental units in the animal world fit between two categories: many offspring, low investment, or low offspring, big investment. With many offspring, not much effort is put in after birth. Why? Effort is energy, and energy is important.

In this case, it’s quantity over quality. Many offspring maximises the chance they’ll besuccessful (success in the natural world means having offspring who can reproduce andcarry your genes on). With fewer offspring, you put more effort in, due to less chance of success.

When thousands of clownfish eggs can be fertilised in one go, Marlin shouldn’t want Nemo to stay at home – he costs more energy than he’s worth. Once they hatch, larval clownfish generally drift on ocean currents, some ending up 120km away from their natal anemones. Once the larval stage ends (about 7 days), they drift to the anemone level tofind a welcoming anemone before they’re eaten.

So why is Marlin so obsessed? Well…

 

Marlin should’ve turned into Marilyn

There’s no way to break this gently.

When Coral died, Marlin, as the dominant male, should have transitioned into a female. Nemo would have become the dominant male and when Marlin was fully transitioned, began reproducing with her.

I’ll give you a moment to take it in.

Clownfish, like some other fish species, are hermaphrodites, meaning they can produce both male and female sex cells. In nonhermaphroditic species only males produce male sex cells (sperm), and only females produce female sex cells (eggs)).

More specifically, they are
sequential hermaphrodites of the protandrous mode they
start life as males and can switch to female. The opposite of this is a protogynous
species, when individuals start as females and can switch to males. The middle? Serial
bidirectional sex changers, where individuals can change multiple times during life.

Not much is known about how this happens from the cellular aspect (
this report has
made some headway), but transitions are commonly triggered by age, size, or social
context.


For clownfish, it’s the lack of a breeding female. The dominant male steps up and begins the transition, leaving the nonbreeding males to increase in rank, with the
largest becoming the new dominant male and establishing hierarchy over the others.
It doesn’t take long for the new male to reach sexual maturation they may even already be sexually mature, but due to the dominant breeding pair, unable to reproduce.
This, by the way, is why all those non-dominant clownfish stick around – they’re waiting for their chance.

Did Nemo ruin it all by being captured?

While the dominant male takes a short period of time to be ready for breeding, the new
female takes longer to transition often years.
This transition is one of the best examples of neuroplasticity, or the nervous system’s ability to change activity in
response to stimuli (internal or external) by reorganising itself.


Within the first 6 months, parts of the brain that control sex organs undergo
cellular change into the female form. During this time, body size grows, and the male
gonads regress to a small amount of testicular tissue that continues to release
testosterone, and a small number of underdeveloped eggs.


At 6 months, all brain changes are complete, and the male is now behaving as a female. Interestingly, despite still having male sex hormones and organs, the other fish now recognise the transitioned fish as a female.

Eventually, the brain sends signals to the gonads to develop fully formed eggs. This can take years, but once it happens, the female is ready to reproduce.

So maybe Marlin fully intended to become Marylin, but Nemo was captured before he
could start the process.

I guess we’ll never know…

 

And that, finally, is the list of reasons Nemo should go find a therapist. And if you feel slightly traumatised by all of this, just remember, these are normal clownfish science things, happening every day in the big blue ocean.

They’re not weird.

…Right?

Author

  • Tamara Tuchin

    Tamara Tuchin has honed her writing skills during intense bouts of procrastination. Oddly enough, her writing has improved dramatically since she started university. After two years of journalism, she suffered a slight quarter-life crisis, and is now heading into her third year of animal science and zoology. You'll find her - you guessed it - procrastinating. Tamara joined the W'SUP editorial team in March 2025. She has a published short story, Dance Baby Dance, and won W'SUP's Editor's Choice Award in 2024.

    View all posts

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