Fish reared in large groups showed more submissive and less aggressive behaviour to big fish in the group, social behaviour which greatly enhances the survival chances of smaller fish
Stefan Fischer
A new study shows that cichlid fish reared in larger social groups from birth display a greater and more extensive range of social interactions, which continues into the later life of the fish. Researchers say this indicates the fish develop more attuned social behaviour as a result of early environments.
The researchers also found that those fish raised in a more complex social environment have a different brain structure to those who experienced fewer group members in early life. If fish experienced the complex social environment for 2 month they had a larger hypothalamus: the area that contains most of the brain nodes of the ‘social behaviour network’. They also had a larger ‘optic tectum’, which processes visual stimuli and could be related to the need to process more visual stimuli in larger groups, say researchers.
The brains of fish with enhanced social skills were not bigger overall than those reared in small groups; however, the ‘architecture’ within the brain was different.
“Our data suggests that, during development, relative brain parts change their size in response to environmental cues without affecting overall brain size: increasing certain parts forces others to decrease concurrently. These ‘plastic’ adjustments of brain architecture were still present long after the early stages of social interaction,” said study author Dr Stefan Fischer, from Cambridge University’s Department of Zoology.
“Social animals need to develop social skills, which regulate social interactions, aggression and hierarchy formations within groups. Such skills are difficult and costly to develop, and only beneficial if the early social environment predicts a high number of social interactions continues to be critically important later in life,” he said.
For the study, published this week in the journal The American Naturalist, researchers used the Neolamprologus pulcher (N. Pulcher) breed of cichlid, primarily found in Lake Tanganyika - the great African freshwater lake that feeds into the Congo River.
Image: Neolamprologus pulcher (N. Pulcher) breed of cichlid fish used in the study
Credit: Dario Josi
Reproduced courtesy of the University of Cambridge