How to make your fish's brain bigger
Scattering a layer of gravel on the bottom of your tank could be enough to increase the size of your fish's brain.
According to a study by scientists at UC Davis in California, the environment that fish experience in their first few weeks can affect the size that different parts of the brain grow to.
It's been widely assumed that the size of a fish's brain is down to natural selection, or to selective breeding over lots of generations. However, a fish's brain grows continuously throughout its life, and scientists believe that this makes the fish brain particularly responsive to environmental conditions experieced during development.
To test the theory, Rebecca Kihslinger and Professor Gabrielle Nevitt undertook a study to see what would happen to the brains of baby trout if they were exposed to different environments during their first few weeks of life.
Wild salmonids typically lay their eggs in stony substrates, and their fry, called alevins, are often buried among the gravel in turbulent and fast-flowing waters.
But, in captivity, they're usually raised in shallow trays, and don't get jiggled around, buried under gravel, or threatened with being washed away.
Bigger brainThe results showed that adding stones to the rearing tanks in which the alevins were kept caused their brains to transform:
"We found that alevins reared with stones grew brains with significantly larger cerebella than genetically similar fish reared in conventional tanks.
"This shift to a larger cerebellar size was, in turn, accompanied by changes in locomotory behaviors - behaviors that correlate strongly to the function of this brain region."
The study also shows that lab-reared fish had smaller brains than hatchery-bred fish reared under natural conditions.
The scientists believe that the environment the fish experience within their first three weeks can result in brain differences that have usually been attributed to genetic selection.
They also go on to suggest that breeders should consider enriching the environment of trout fry when designing captive breeding facilities or conservation projects.
Their findings have just been reported in the Journal of Experimental Biology.
For more details see the paper: Kihslinger RL, Nevitt GA (2006) - Early rearing environment impacts cerebellar growth in juvenile salmon. J Exp Biol. 2006 Feb 1;209(Pt 3):504-9.