EVIDENCE FOR MYOBLASTS CONTRIBUTING PREFORMED ACTIN AND MYOSIN TO DEVELOPING MUSCLE IN THE DIPTERAN INSECT NEOBELLIERIA-BULLATA

1. Rhodamine labelled phalloidin staining, electrophoresis, polarizati on microscopy and electron microscopy were used to study the presence, distribution and organization of actin and myosin in a special kind o f vesicles which are abundantly present in pupal haemolymph of Neobell ieria (Sarcophaga) bullata. 2. In such vesicles actin and myosin can o ccur in a clearly polarized way. 3. Groups of filamentous actin and my osin containing vesicles seem to align themselves in between growing m yofibers of developing flight muscles and gut musculature. 4. It is su ggested that these vesicles are developing myoblasts which directly co ntribute actin and myosin, either separately or organized as actomyosi n, to forming muscle.