Mosaic animals in which the retina is homozygous for sd-310 (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-310 shows activity-dependent loss of the off transient only. Hemizygotes and homozygotes die as pharate adults.