THE DEVELOPMENT OF INDIRECT FLIGHT-MUSCLE INNERVATION IN DROSOPHILA-MELANOGASTER

We have examined the development of innervation to the indirect flight muscles of Drosophila. During metamorphosis, the larval intersegmental nerve of the mesothorax is remodelled to innervate the dorsal longitudinal muscles and two of the dorsoventral muscles. Another modified larval nerve innervates the remaining dorsoventral muscle. The dorsal longitudinal muscles develop using modified larval muscles as templates while dorsoventral muscles develop without the use of such templates. The development of innervation to the two groups of indirect flight muscles differs in spatial and temporal patterns, which may reflect the different ways in which these muscles develop. The identification of myoblasts associated with thoracic nerves during larval life and the association of migrating myoblasts with nerves during metamorphosis indicate the existence of nerve-muscle interactions during indirect flight muscle development. In addition, the developing pattern of axonal branching suggests a role for the target muscles in respecifying neuromuscular junctions during metamorphosis.