Ecotype differences in aggression, neural activity and behaviorally relevant gene expression in cichlid fish

Area of Science:

• Evolutionary biology
• Neuroscience
• Genomics

Background:

• Lake Malawi cichlids exhibit rapid adaptive radiation, forming distinct rock-dwelling (Mbuna) and sand-dwelling ecotypes.
• Mbuna are territorial, while sand-dwelling species form leks, indicating significant behavioral divergence.
• The genetic underpinnings of these behavioral differences, particularly aggression, remain largely unknown.

Purpose of the Study:

• To investigate the genomic basis of phenotypic variation in aggression between rock-dwelling and sand-dwelling cichlid ecotypes.
• To compare behavioral, neural, and gene expression differences related to aggression in representative cichlid species.

Main Methods:

• Behavioral assays quantifying mirror-elicited aggression across seven cichlid species.
• Comparative analysis of neural activity during aggression in two distinct ecotypes (Mchenga conophoros and Petrotilapia chitimba).
• Differential gene expression analysis in neurons activated during aggression between the two ecotypes.

Main Results:

• Significant ecotype and species-specific differences in mirror-elicited aggression were observed.
• A substantial number of genes showed differential expression related to aggression and between ecotypes.
• Key genes identified include neuropeptides, steroid hormone synthesis genes, and neurotransmitter-related genes.

Conclusions:

• The study identifies candidate genes potentially responsible for evolved behavioral differences in cichlid aggression.
• These findings establish a foundation for future research into the neurogenomic basis of species divergence in cichlids.
• This work highlights the utility of cichlids as a model system for studying the evolution of brain and behavior.