Sexual dimorphism matches photoreceptor performance to behavioural requirements

Differences in behaviour exist between the sexes of most animal species and are associated with many sex-specific specializations. The visual system o f the male housefly is known to be specialized for pursuit behaviour that c ulminates in mating, Males chase females using a high-acuity region of the fronto-dorsal retina (the 'love spot') that drives sex-specific neural circ uitry We show that love spot photoreceptors of the housefly combine better spatial resolution with a faster electrical response, thereby allowing them to code higher velocities and smaller targets than female photoreceptors. Love spot photoreceptors of males are more than 60% faster than their femal e counterparts and are among the fastest recorded for any animal. The super ior response dynamics of male photoreceptors is achieved by a speeding up o f the biochemical processes involved in phototransduction and by a tuned vo ltage-activated conductance that boosts the membrane frequency response. Th ese results demonstrate that the inherent plasticity of phototransduction f acilitates the tuning of the dynamics of visual processing to the requireme nts of visual ecology.