We will explore the hyperdiverse cichlid fishes of Lake Tanganyika as a novel model system to study sleep ecology and genetics. Many of the molecular and neuronal mechanisms that regulate the circadian phase, duration, and structure of sleep are conserved across vertebrates. Given this extensive conservation, it is remarkable that sleep displays extensive variation across and even within species. Species can sleep as little as 2 hrs a day (giraffes), or as much as 20 hrs (bats), they can be active during different times of the day (nocturnal or crepuscular predators) or display place preferences for where they sleep (in nests or burrows). Species-specific variations in sleep features like where and when they sleep, or how long and how frequently they sleep may be adaptive. Changes in sleep, or temporal niche differentiation, could allow exploitation of new ecological niches. Temporal adaptation can allow animals to avoid predators (or encounter prey), or to reduce competition with similar species over resources. However, the genetics and ecology underlying sleep diversity across and within species are largely unknown.Cichlids represent the most extraordinary example of vertebrate explosive speciation - approximately 2000 species have evolved within the last 10 million years in the Rift Valley Lakes of Africa. In these lakes, cichlids have diversified to take up the majority of ecological niches, diversifying in diet, body size, mating behaviours, colouration, and habitat preferences. These ecological adaptations are partially driven by behavioural changes, though no studies to date have examined the role of temporal niche adaptation and sleep in cichlids. We therefore hypothesise that cichlid diversity is a powerful system to uncover the genetic basis of sleep diversity and its connection with ecological diversity.Aim 1: Characterise the natural variation in sleep behaviour and ecology in Lake Tanganyikan cichlids. We will undertake an extensive screen of sleep behaviours across at least 60 of the ~240 cichlid species in Lake Tanganyika. For each species we will determine: the circadian phase of activity (when they sleep), the sleep structure (frequency and duration of sleep bouts), and circadian or state dependent changes in place preference (where they sleep). These characteristics will be correlated with known ecologies for each species. For example, predatory cichlids may have evolved to be active when their prey species are asleep. Other species might migrate between environments, or retreat to the safety of rocky substrates between sleep and wake periods. These studies will reveal whether and how sleep behaviors reflect ecological niches.Aim 2: Determine the genetic architecture of sleep-associated behaviours in Lake Tanganyikan cichlids. Across lakes, cichlids have convergently evolved many traits and are predicted to have done so using similar genetic mechanisms. We hypothesize that shared sleep behaviors evolved through similar genetic changes. From our collaborators we currently have access to whole genome sequences from all of the ~240 species of cichlids in Lake Tanganyika (approximately 1000 total genomes), and brain transcriptomes from 76 species. We will use these resources to perform genome wide association studies (GWAS) to identify genomic variants associated with specific sleep features. These analyses will lay the foundation for future work - we will follow up with high-resolution genetic mapping and molecular characterization of the genes and variants we identify.This project will be the first to explore the remarkable power of the cichlid system to interrogate the mysterious relationships between sleep and ecology, and would establish them as a novel model system to study sleep. Connecting specific sleep behaviors to specific ecological niches would provide fundamental insights into animal behaviors in natural habitats. Linking specific sleep behaviors to genomic loci would help reveal the genetic basis of animal sleep and have potential relevance to the genetics of sleep in humans.