Under ideal growth conditions, homozygotes develop into morphologically normal adults with profound behavioural deficits. Mutant males rarely successfully mate with wild-type females. When presented with wild-type or Adar^- females, mutant males do not initiate any displays of courtship. Homozygous females can be mated by wild-type males and give rise to morphologically normal hemizygous males which show the mutant adult behavioural defects. The time course of development from egg-laying to pupariation and from the onset of pupariation to eclosion is not significantly different from wild type in mutant animals. There is a slight reduction in viability through adulthood compared to wild type. Mutant larvae appear normal for locomotion, respond to stimuli and are normal in a phototactic behaviour assay. Mutant adults show severe neuro-behavioural phenotypes. They show uncoordinated locomotion, occasional tremors and varying degrees of abnormal body posture immediately upon eclosion. Mutant adults spend an inordinate amount of time grooming compared to wild type. This obsessive cleaning is apparent throughout the lifetime of the animal. Mutants are capable of flying and jumping but do so only when repeatedly provoked and then only rarely. Flight in these animals is erratic. Flies recover more slowly from ether anesthesia. They show a strong temperature-dependent of behavioural defects resulting in bouts of paralysis and extreme motor uncoordination at the restrictive temperature. The behavioural phenotypes become more severe with age and some new phenotypes appear. Tremors increase dramatically such that locomotion is severely compromised in animals beyond day 50. Animals fall over and become increasingly inefficient at righting themselves. Many animals beyond day 30 show circling behaviour that varies from wide circling to circling while standing in place. A majority of animals beyond day 50 show a persistent upheld wing phenotype. Marked asymmetries appear in the animals, manifesting as one upheld wing or leg, extension of one or both back legs and more severe asymmetries in posture. The photoreceptors appear disorganised and extend longitudinally, projecting further to reach the laminar layer in mutants (rather than the more compact, organised retinal structure seen in wild-type flies). Young (1-3 day) mutant brains appear grossly normal. However, lesions appear by day 30 and are distributed randomly in the central brain, optic lobes and retina. The lesions appear as vacuolated regions and are most prevalent in the retina, lamina and optic lobes. Vacuoles appear to increase in size and number with age, and by day 50, animals can be found with extensive brain degeneration. Mutant adults do not have a reduced life span but are at an extreme selective disadvantage, showing a high mortality rate with respect to wild-type animals in mixed populations, even under relatively low population density.