The remaining fish were kept in their tanks and unexposed to further disturbance for an additional 11 days until they were also removed for analysis.
The results showed that fish brains grow when repeatedly exposed to predation cues, but revert when those cues are removed. Researchers can’t determine if the reversion is due to slowed brain growth or if it’s the result of the rest of the fish’s body catching up now that it has extra energy.
“We predicted this reversal because neurogenesis — the production of neurons in the brain that causes it to grow — is energetically very costly,” Brown explains. If an animal does not need to produce extra neurons as a survival mechanism, it will use this energy to grow in size, strength, and sexual maturity. This, says Brown, suggests reversible neuroplasticity. The study builds on work by Brendan Joyce, a PhD student in Brown’s lab, who showed similar changes in brain morphology in adult redbelly and juvenile Atlantic salmon.
“Twenty years ago, evolutionary biologists looked at behavioral decisions and said, ‘The animal will do this or that.’ But it is more probably the case of “L’animal box do this or do that,” depending on the environmental cues it receives,” Brown adds. “Variations in environment, food availability, mating, predation – all of these factor into and shape how an animal distributes its energy. And that’s the idea of plasticity.
Financial support for this study was provided by the Natural Sciences and Engineering Research Council of Canada, Discovery Grants Program.
Read the quoted article:Predation cues lead to rapid changes in brain morphology of juvenile convict cichlids (Amitatlania nigrofasciata).”