The presynaptic morphology of motor terminals is abnormal at the mutant neuromuscular junction; the motor terminals maintain a flattened growth cone-like structure and fail to constrict into normal synaptic varicosities.

Homozygotes die as late embryos that are unable to hatch. The embryos appear anatomically grossly normal, but are unable to crawl when removed from the chorion and vitelline membrane. The head is capable of some coordinated movements, but the abdominal body wall muscles only fibrillate and there are no coordinated peristaltic waves.