Fig. 7. Ttk is required for proper luminal cuticle formation. Transmission electron microscopy (TEM) micrographs of late-stage embryos. (A,B) Longitudinal sections of the dorsal trunk (DT). Notice the taenidial folds (t) and the cuticle layers - envelope (env), epicuticle (epi) and procuticle (p) - within each taenidium. (B) ttk mutants show a disorganised taenidial structure and density differences at the level of the procuticle. (C,D) Detail of septate junctions (SJs; arrows) between adjacent DT cells. As in wild type (C), SJs are correctly positioned in ttk mutants. (E,F) Detail of the epidermal cuticle. In the procuticle (p) of wild-type embryos (E), the chitin laminae are arranged in a typical helicoidal pattern. In ttk mutants (F) the procuticle is very disorganised. Scale bars: 200 nm.