Homozygotes die during the third larval instar or early pupal stages. Homozygous larvae are sluggish compared to control larvae at 24^oC, but display no obvious morphological defects. There is a 66% decrease in the amplitude of the excitatory junctional potential (EJP) in the muscle at the larval neuromuscular junction compared to control larvae. There is also a decrease in the frequency of spontaneous miniature EJPs in the absence of nerve stimulation. The morphology and number of synaptic boutons appears normal. Rop^G11/Rop^A19 larvae have a similar phenotype. Heterozygous larvae show a 35% decrease in EJP amplitude.

Homozygotes die as embryos at 27^oC and larvae at 25^oC. ERGs of heterozygotes demonstrate a reversible block in synaptic transmission, the viability of photoreceptor cells and lamina cells is not affected as they recover at the permissive temperature.