Effect of x-irradiation on the formation of the puparium in the fleshfly, Sarcophaga bullata

Post-feeding, pre-critical stage larvae (36 hr before pupariation) of Sarcophaga bullata were exposed to X-rays and the effects on pupariation observed. With doses ranging from 1250 to 10,000 R the prepuparial period was prolonged and the duration of this delay increased with higher doses. Doses above 2500 R inhibited the retraction of anterior segments, longitudinal contraction and cuticular shrinkage resulting in larval-like tanned puparia. With the anterior part of the body shielded during irradiation, normal puparia were formed, but after a delay proportional to the area irradiated. Injection of β-ecdysone counteracted this delay. With the doses used, irradiation had no effect on post-critical stage larvae. This suggested that the CNS has a special mechanism which controls the neuromuscular processes of pupariation, and when this mechanism is damaged by irradiation larval-like puparia are formed. The pupariation delay was attributed to a temporary block in the synthesis, or release, or both of α-ecdysone (in whole-body or anteriorly only irradiated larvae) and its final conversion to β-ecdysone (in posteriorly only irradiated larvae). The fact that post-critical stage larvae are insensitive to irradiation suggests that the neuromuscular and neurosecretory processes which are affected by irradiation are already completed at that stage.