Data from: Experimental evidence for sex-specific plasticity in adult brain

Background: Plasticity in brain size and the size of different brain
regions during early ontogeny is known from many vertebrate taxa, but less
is known about plasticity in the brains of adults. In contrast to mammals
and birds, most parts of a fish’s brain continue to undergo neurogenesis
throughout adulthood, making lifelong plasticity in brain size possible.
We tested whether maturing adult three-spined sticklebacks (Gasterosteus
aculeatus) reared in a stimulus-poor environment exhibited brain
plasticity in response to environmental enrichment, and whether these
responses were sex-specific, thus altering the degree of sexual size
dimorphism in the brain. Results: Relative sizes of total brain and bulbus
olfactorius showed sex-specific responses to treatment: males developed
larger brains but smaller bulbi olfactorii than females in the enriched
treatment. Hence, the degree of sexual size dimorphism (SSD) in relative
brain size and the relative size of the bulbus olfactorius was found to be
environment-dependent. Furthermore, the enriched treatment induced
development of smaller tecta optica in both sexes. Conclusions: These
results demonstrate that adult fish can alter the size of their brain (or
brain regions) in response to environmental stimuli, and these responses
can be sex-specific. Hence, the degree of SSD in brain size can be
environment-dependent, and our results hint at the possibility of a large
plastic component to SSD in stickleback brains. Apart from contributing to
our understanding of the processes shaping and explaining variation in
brain size and the size of different brain regions in the wild, the
results show that provision of structural complexity in captive
environments can influence brain development. Assuming that the observed
plasticity influences fish behaviour, these findings may also have
relevance for fish stocking, both for economical and conservational
purposes.