The Na+/K+-ATPase β subunit Nrv3 is essential for the function and survival of Drosophila photoreceptors. Na+/K+-ATPase β subunits Nrv1, Nrv2 and Nrv3 were separately knocked down in photoreceptors. A, ERG recordings revealed that the light response in both 1-day and 10-day-old Nrv3 knockdown flies was impaired. No ERG defect was observed in either the control GMR-Gal4 flies or the Nrv1 and Nrv2 knockdown flies. B, Optical neutralization assays showed a severe loss of peripheral rhabdomeres in 10-day-old Nrv2 knockdown flies but not in 1-day-old flies. C, The amplitude of the ERG response was reduced to a similar extent in 1-day-old and 10-day-old Nrv3 knockdown flies. D, The rhabdomere integrity index was dramatically decreased in 10-day-old Nrv3 knockdown flies. E, Nrv3 knockdown flies had normal phototaxis but exhibited a weaker optomotor response. There were no significant differences within genotypes between 1-day-old and 10-day-old flies. Asterisk (*): p< 0.01; Two-tailed t-test. Error bars denote S.E.M.