Under control conditions, rtp¹ homozygous third instar larvae do not display significant changes in the number of sensory axons per nerve, as compared to controls.

Response termination to light stimulus of dark-adapted retin¹ mutant retinas is slower that that in wild-type flies. In contrast to 3 day old mutants, retinas of 7 day old homozygous retin¹ as well as Df(3R)ED5147/retin¹ mutants display prolonged depolarization afterpotential (PDA) compared with wild-types. The reduced PDA does does not appear to be attributable to an age-dependent loss of the rhabdomeres, because 7-day old retin¹ flies retain the full complement of rhabdomeres, although the size of rhabdomeres declines slightly. Maintaining the flies in the dark does not fully suppress this phenotype, although there is a minor improvement.