Fig. 5. Electron micrographs of opener muscle from immature (A) and allatectomised (B,C,D) females. (A,C) Overview of myofibril structure. Note the abundance of tracheoles (Tr) surrounding the myofibrils and the similarity of basic organisation and structure of muscle elements in immature and allatectomised females. (B,D) Transverse (B) and longitudinal (D) sections of muscle fibres obtained from allatectomised females reveal the presence of dyads (open arrow in B) and numerous microtubules (MT in B), almost comparable to those seen in immature female fibres (compare to Fig. 4C). However, elements of the sarcoplasmic reticulum (SR) surrounding the myofibrils and mitochondria (M) appear somewhat better organised and larger when compared to fibres of immature females. Ab, A-band; Ib, I-band; N, nucleus; Z, Z-line. Scale bars, 1 µm (A,C,D); 0.25 µm (B).