Mutant animals exhibit extensive central nervous system degeneration. Brains from aged adults show highly penetrant and extensive vacuolisation, especially prominent in the optic lobes but extending into the central brain as well. Vacuolisation is also evident throughout the entire thoracic ganglion of mutant flies. The onset of neurodegeneration is age dependant. Third instar larvae do not reveal any obvious neuropathology, and young adult flies do not differ noticeably from the wild-type. This neuropathology is not light dependant. Mutant larvae become paralysed at 38[o]C. This paralysis is reversed upon return to 21[o]C. Younger adults do not show overt temperature sensitive paralysis. The life span of mutants kept at 28[o]C is half of the wild-type controls. They also have sluggish locomotor activity at 20-22[o]C which becomes more pronounced as the flies age, taking up to double the time to complete a simple horizontal locomotion test than wild-type controls of the equivalent age. Young and older mutants flies all fail in a climbing test and exhibit considerably reduced flight ability. Electroretinogram (ERG) readings in mutants appear almost normal at 20 and 37[o]C, however, 20[o]C recurrent spikes appear before during and after light exposure. At 34-37[o]C these become more prominent bursts of apparent activity.