Meeting Abstract
In Lake Malawi, two ecologically distinct lineages of cichlid fishes (rock- versus sand-dwelling ecotypes, each comprised of over 200 species) evolved from a single ancestral population 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. First, we demonstrate species and ecotype differences in behavior using mirror-elicited aggression tests in seven species. We find that, in general, rock-dwelling species attack their reflection faster and perform more frontal attacks. In contrast, sand species perform more lateral displays (orienting laterally and displaying their colors). Second, using one rock species (Petrotilapia chtimba, Petro), and one sand species (Mchenga conophoros, MC), we compare neural activity following mirror-elicited aggression in three brain regions with known roles in aggression in fish: Dorsal medial telencephalon (Dm), dorsolateral telencephalon (DI), and the preoptic area (POA). Finally, we use phosphorylated ribosome immunoprecipitation of mRNA from whole brain followed by RNA-sequencing to compare the gene expression patterns of neurons activated by mirror-elicited aggression across the two species. Due to their recent evolutionary divergence, multiple rock and sand species have been hybridized in the lab. Thus, 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.
