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

• Type of Material: Article
• Authors: Nicole Baran, Emory University; J. Todd Streelman, Georgia Institute of Technology
• Language: English
• Date: 2020-05-08
• Publisher: Wiley
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2020 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society
• Final Published Version (URL): https://dx.doi.org/10.1111%2Fgbb.12657
• Title of Journal or Parent Work: GENES BRAIN AND BEHAVIOR
• Volume: 19
• Issue: 6
• Grant/Funding Information: This work was supported by NIH Grants R01GM101095 (to J.T.S.) and F32GM125496 (to N.M.B.)
• Keywords: social behavior; PhosphoTRAP; neural induction; aggression; evolution; Cichlid fish; RNA-seq; gene expression; species difference; pS6

Abstract

In Lake Malawi, two ecologically distinct lineages of cichlid fishes (rock- versus sand-dwelling ecotypes, each comprised of over 200 species) evolved within the last million years. The rock-dwelling species (Mbuna) are aggressively territorial year-round and males court and spawn with females over rocky substrate. In contrast, males of sand-dwelling species are not territorial and instead aggregate on seasonal breeding leks in which males construct courtship “bowers” in the sand. However, little is known about how phenotypic variation in aggression is produced by the genome. In this study, we first quantify and compare behavior in seven cichlid species, demonstrating substantial ecotype and species differences in unconditioned mirror-elicited aggression. Second, we compare neural activity in mirror-elicited aggression in two representative species, Mchenga conophoros (sand-dwelling) and Petrotilapia chitimba (rock-dwelling). Finally, we compare gene expression patterns between these two species, specifically within neurons activated during mirror aggression. We identified a large number of genes showing differential expression in mirror-elicited aggression, as well as many genes that differ between ecotypes. These genes, which may underly species differences in behavior, include several neuropeptides, genes involved in the synthesis of steroid hormones, and neurotransmitter activity. This work lays the foundation for future experiments using this emerging genetic model system to investigate the genomic basis of evolved species differences in both brain and behavior.