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My name is Justin Rhodes and I study behavioral neuroscience.
We have chosen a model organism that shows you
a very dramatic example of a social environment having long lasting impact on the behavior
and physiology of the organism. As a model system, to understand how the brain orchestrates this...
And these are clownfish, which change sex depending on the social environment.
We have clownfish paired off in twenty six tanks:
one male, one female, and maybe a couple of
other smaller undifferentiated fish, living on sea anemones.
And the larger one is always female, dominant,
and the second in the hierarchy is the male
and if you remove the female,
then the male will change sex and become a female in a matter of couple of months.
And basically this is through the brain interpreting this social change.
The clown fish has both testicular tissue and ovarian tissue
and so it is a matter of just encouraging one of the other tissues to develop.
It is unclear exactly what signals are using, probably mostly vision, and
maybe some olfaction and maybe even sound and that
probably communicates to the
hypothamlamus and areas in the brain that we know communicates to the pituitary
gland, which is a little gland right below the brain which releases hormones into the blood,
which communicate to the gonads, causing
testes to absorb and ovaries to develop and morphology to change and
completely reverse the behaviors, because this used to be a male
but now it is dominant and behaving like a female and so on.
One hypothesis is that a sex change will involve some reorganization of the brain
and we can measure and track, when we remove the female, and observe what changes take
place in the brain of that male changing sex in female. We can see what areas
of the brain are sprouting new neurons or what areas of the brain are removing new neurons; We can
discover, then, how in this one dramatic example of how the
social environment reorganizes behavior and
presumably make some inferences. The two human implications potentially are
humans also have a similar...
they don't change sex but social environment can have long-lasting effects on
their behavior and personality. Presumably, this involves similar biology. Another
potential implication of this work is identifying
changes in the brain that apparently are necessary to function as a female
versus a male; if you measure male and female brains, you see differences.
The question is: which of those differences are functional? What are the
neuro-anatomical or physiological differences between a male and a female brain that
makes males behave like males, and females behave like females difficult
to know when you compare males and females and in different species.
But, in a sex changing fish, presumably those changes that are actually undergoing
reorganization, new neurons sprouting up in one area, neurons degrading in another area,
those are most likely going to be functional because that's going to be very energetically
costly to be able to start rearranging the brain and connections and so on.
If you think about what is happening here,
the fish is just detecting sensory,
a change in the social environment, and somehow that is affecting
basically the whole... the testes to be changed, ovaries to develop,
the animals to get larger, the behavior to change, genitalia is changing,
so this is a really remarkable
example of how your experience, your social experience,
can have long lasting behavior and effects on your behavior and personality and
morphology really, anatomy, in this species.
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