The metamorphosis of the humeral disc ofDrosophila melanogaster

✍ Scribed by Pedelty, Joey ;Arking, Robert

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 769 KB
• Volume: 216
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402160115

✦ Synopsis

Abstract

The metamorphosis of the Drosophila humeral (dorsal prothoracic) disc was examined using histological procedures as well as both in vivo and in vitro culture techniques. The histological analysis was done at four developmental stages: late third instar larvae, early pre‐pupae, late pre‐pupae, and early pupae. In the late third instar larva, the disc forms a cylinder around the tracheal tubule just posterior to the anterior spiracles and consists of an outer layer of imaginal cells and an inner layer of larval cells. Evagination of the disc begins in the early prepupal stage and consists of a marked medial and posterior migration of the imaginal cells along each of the lateral tracheal trunks. By the late prepupal stage the disc has come into contact with the evaginating wing disc and has formed two structures, an anterior tubular structure which will form the second thoracic spiracle (SpTh~2~) and a posterior multilayered spherical structure which will form the single layered humeral callus of the adult. By the early pupal stage the humeral callus has become integrated with the rest of the thorax and the SpTh~2~ is contiguous with the developing adult tracheal system. In vitro cultures also showed a marked posterior migration of the imaginal cells along the tracheal trunk during the first 20–24 hours of culture which corresponds to the normal evagination period of cultured wing and leg discs. No resulting apolysis or differentiation of the cultured humeral discs was observed. Only a low level of differentiation was obtained following the in vivo culture of humeral discs. In both culture experiments, normal levels of differentiation were exhibited by the control (ventral prothoracic) discs. A hypothesis involving the possible requirement of humeral disc‐wing disc contact as a prerequisite for differentiation is presented.