1 Social and ecological regulation of a decision - making circuit

38 Ecological context, sensory inputs, and the internal physiological state are all factors 39 that need to be integrated for an animal to make appropriate behavioral decisions. 40 However, these factors have rarely been studied in the same system. In the African 41 cichlid fish Astatotilapia burtoni, males alternate between two phenotypes based on 42 position in a social hierarchy. When dominant (DOM), fish display bright body coloration 43 as well as a wealth of aggressive and reproductive behavioral patterns that make them 44 conspicuous to predators. Subordinate (SUB) males, on the other hand, decrease 45 predation risk by adopting cryptic coloration and schooling behavior. We therefore 46 hypothesized that DOMs would show enhanced startle-escape responsiveness to 47 compensate for their increased predation risk. Indeed, behavioral responses to sound 48 clicks of various intensities revealed a significantly higher mean startle rate in DOMs as 49 compared to SUBs. Electrophysiological recordings from the Mauthner cells (M-cells), 50 the neurons triggering startle were performed in anesthetized animals and revealed 51 larger synaptic responses to sound clicks in DOMs, consistent to the behavioral results. 52 In addition, the inhibitory drive mediated by interneurons (PHP cells) presynaptic to the 53 M-cell was significantly reduced in DOMs. Taken together, the results suggest that the 54 likelihood for an escape to occur for a given auditory stimulus is higher in DOMs due to 55 a more excitable M-cell. More broadly, this study provides an integrative explanation of 56 an ecological and social trade-off at the level of an identifiable decision-making neural 57