The Journal of Neurophysiology Vol. 85 No. 1 January 2001, pp. 98-104
Copyright ©2001 by the American Physiological Society

Alterations in Development, Behavior, and Physiology in Drosophila Larva That Have Reduced Ecdysone Production

 ¹School of Biological Sciences, University of Kentucky, Lexington 40506-0225; and  ²Graduate Center for Toxicology, Chandler Medical Center, University of Kentucky, Lexington, Kentucky 40506-0305

Li, Hao, Doug Harrison, Grace Jones, Davy Jones, and Robin L. Cooper. Alterations in Development, Behavior, and Physiology in Drosophila Larva That Have Reduced Ecdysone Production. J. Neurophysiol. 85: 98-104, 2001. We investigated behavior, physiology, sensitivity to exogenous application of ecdysone, and nerve terminal structure for differences between the reduced ecdysone genotype, ecd¹/ecd¹, and wild-type control ecd¹/TM6B animals during the early and late third instars when raised at 25°C. The ecd¹ mutants were able to survive through larval development and form pupae. However, the results demonstrate that the time to pupation is lengthened by about 50 h for the ecd¹/ecd¹ as compared with the wild-type control siblings. In addition to the lengthened larval cycle in the mutant, ecd¹/ecd¹ animals, they also display behavioral differences as compared with controls. The rate of body wall contraction and mouth hook movements are reduced in the early third instar of ecd¹/ecd¹ as compared with controls. 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 reduced in the late third instars for controls. Application of exogenous ecdysone is still effective during the late third instar for the ecd¹/ecd¹ but not the controls. This suggests that endogenous production of ecdysone have already taken place in the wild-type but not the ecd¹/ecd¹ larvae, thus the rapid nongenomic responses could still be observed in the late third ecd¹/ecd¹ larvae. Structurally the number of varicosities and the terminal length showed significant differences between ecd¹/ecd¹ and the wild-type ecd¹/TM6B genotype in the late third instars.