Mosaic animals in which the retina is homozygous for sd-1119 (generated using the "EGUF/hid" system) have normal external eye morphology but show defects in a phototaxis assay. The electroretinogram of mosaic animals in which the retina is homozygous for sd-1119 has a defective on transient and activity-dependent loss of the off transient. Photoreceptor axon projection patterns in these animals are essentially indistinguishable from controls. Homozygotes die as first-second instar larvae.