부산대학교 도서관

The role of 20-hydroxyecdysone (20E) in the metamorphosis of the central nervous system was investigated by recording feeding, wandering and pupariation behaviour as the measures of hormonal effects on the neural tissues in the flesh fly Neobellieria (Sarcophaga) bullata. The minimum amount of food essential for the commitment to metamorphosis is rather small and constant and the larvae ingest it during the first 4 to12 h of the last instar. Underfed larvae maintain food appetency for a certain time and this period of hunger can be considerably shortened by the application of 20E. Application of 20E also significantly shortens or abolishes the intake of additional food offered to starving larvae. Thus 20E has an effect on neural mechanisms controlling both termination of the period of hunger and suppression of feeding behaviour. Application of 20E at any time during the wandering stage stimulates the precocious onset of pupariation. The central neurons controlling motor patterns of pupariation behaviour are committed to perform properly their programme some 15 h earlier than the larval integument is ready to transform into normal puparium. As a result of this temporal shift of tissue determination, some precociously formed puparia are not properly shaped despite the fact that the larva is exhibiting normal patterns of pupariation behaviour.