Alterations in development, behavior, and physiology in Drosophila larva that have reduced ecdysone production

We investigated behavior, physiology, sensitivity to exogenous application of ecdysone, and nerve terminal structure for differences between the reduc ed ecdysone genotype, ecd(1)/ecd(1), and wild-type control ecd(1)/TM6B anim als during the early and late third instars when raised at 25 degreesC. The ecd(1) mutants were able to survive through larval development and form pu pae. However, the results demonstrate that the time to pupation is lengthen ed by about 50 h for the ecd(1)/ecd(1) as compared with the wild-type contr ol siblings. In addition to the lengthened larval cycle in the mutant, ecd( 1)/ecd(1) animals, they also display behavioral differences as compared wit h controls. The rate of body wall contraction and mouth hook movements are reduced in the early third instar of ecd(1)/ecd(1) as compared with control s. The physiological measure of excitatory junction potential amplitude for the combined Is and Ib terminals did not reveal any differences among the two genotypes during the early third instar but the synaptic strength is re duced in the late third instars for controls. Application of exogenous ecdy sone is still effective during the late third instar for the ecd(1)/ecd(1) but not the controls. This suggests that endogenous production of ecdysone have already taken place in the wild-type but not the ecd(1)/ecd(1) larvae, thus the rapid nongenomic responses could still be observed in the late th ird ecd(1)/ecd(1) larvae. Structurally the number of varicosities and the t erminal length showed significant differences between ecd(1)/ecd(1) and the wild-type ecd(1)/TM6B genotype in the late third instars.