Integument and sensory nerve differentiation ofDrosophila leg and wing imaginal discs in vitro.

An ultrastructural analysis is presented of the cuticular and neural structures formed by the prothoracic leg and wing imaginal discs of maleDrosophila melanogaster larvae during culture in vitro with 0.2 μg/ml of β-ecdysone. A pupal cuticle, and subsequently an imaginal cuticle with a well-defined epicuticle and a laminated endocuticle is formed. The ultrastructure of the epidermis and of cuticular structures such as bristles, trichomes, apodemes, and tracheoles is very similar to that found in situ. Dendrites and nerve cell bodies are formed in vitro, and sensory axons form nerve bundles similar to those of normal appendages in situ, despite their isolation from the central nervous system. It is concluded that at the ultrastructural level, differentiation in vitro closely parallels the normal course of development.