Fig. 1. Effect of the Drosophila tendrils mutation on lumen formation in the terminal branches of the tracheal system. Terminal branches are formed by long cytoplasmic projections of tracheal terminal cells that develop a single membrane bound lumen within each projection (top left panel). In tendrils mutant terminal cells (top right and bottom panels), multiple convoluted lumina are seen within individual projections. Image courtesy of Boaz Levi, Amin Ghabrial and Mark Krasnow (Stanford University School of Medicine, Stanford, CA, USA).