From the WashU Newsroom…
Helmet-heads of the freshwater fish world, African mormyrid fishes are known for having a brain-to-body size ratio that is similar to humans.
But there’s actually a great deal of variation in the size of mormyrid brains. These differences provide an opportunity to look at what’s behind the bulk.
Researchers from Washington University in St. Louis have mapped the regions of the brain in mormyrid fish in extremely high detail. In a new study published in the Nov. 15 issue of Current Biology, they report that the part of the brain called the cerebellum is bigger in members of this fish family compared to related fish — and this may be associated with their use of weak electric discharges to locate prey and to communicate with one another.
The size finding in itself is not particularly surprising for those who follow this fish, said Bruce Carlson, professor of biology in Arts & Sciences. “It had almost become a truism,” he said. In mormyrids, at least, the thinking went, “big brains mean big cerebellums.”
Instead, the researchers are charged up about how their new measurements can help illuminate longstanding questions in neuroanatomy.
As brains get bigger, do all regions of the brain scale up in a predictable way? Or does natural selection act independently on separate regions of the brain — such that certain parts of the brain become enlarged in animals that have extra reasons to use them?