Fish Schooling Ability Determined by Genetic Factors

Genetic factors influence whether fish swim in schools and how well they do it, according to new research published in the journal Current Biology, which suggests that by better understanding the genomic foundations of social behavior in fish, the closer we will be to understanding how genes drive human behavior.

A team of researchers from the Human Biology division of Fred Hutchinson Cancer Research Center in Seattle, Wash. studied the threespine stickleback, a small fish native to the Northern Hemisphere.

"The motivation to be social is common among fish and humans," said lead study author Anna Greenwood. "Some of the same brain regions and neurological chemicals that control human social behavior are probably involved in fish social behavior as well."

Previous research on sticklebacks found that a group of the fish from the Pacific Ocean off the coast of Japan schooled strongly, where another group of the fish from a lake in British Colombia seemed to prefer hiding and did not demonstrate an ability to maintain the precisely parallel movements required for schooling. Though both groups of the fish were raised in identical lab settings, they still demonstrated differences in schooling, which Greenwood said "suggests there is some kind of genetic factor controlling this difference."

For the latest research, Greenwood and her colleagues studied lab-raised hybrids of the strongly schooling sticklebacks and the schooling-averse sticklebacks that live in freshwater.

Fish school in order to protect themselves from predators as well as to make swimming more efficient. In the wild, schools of fish were dynamic and fluid, but getting the fish to school in a lab setting was a challenge. The researchers used plastic models of the fish that were affixed to a bicycle tire in a tank of water. The researchers learned that eight is the minimum number of fish needed to initiate a schooling movement.

By examining the fish in a lab setting, the researchers were able to determine that the same genomic regions appear to control the fishes' ability to school as well as the anatomy of the lateral line, the system that allows the fish to detect movement and vibration in water.

Greenwood said their research leads them to believe that just a singe gene can be responsible for fish detecting their environment differently and supports the notion that schooling behavior is controlled in part by the lateral line.

"If we can understand the process by which evolution works and the genes that tend to be affected during evolution in these other model systems, we can apply that to humans," she said.