ato1/ato2 antenna have a small number of coeloconic sensilla. The antennal lobes have normal glomeruli and the inter-antennal commissure is present. The elaboration of glial cell processes within the antennal lobe is normal.
ato1/ato2 flies have severely reduced eyes, which nevertheless contain ommatidia (approximately 200-300 in males, 5-15 in females). The ommatidia mostly contain fewer photoreceptors than wild type. The photoreceptor clusters are variably reduced, containing from 1-8 photoreceptors and any or all of the recruited photoreceptors can be affected. Photoreceptor axons navigate to the optic stalk poorly. This axon pathfinding defect is more severe in females. Those axons that reach the optic stalk are able to continue to their target sites within the optic lobe.