STRUCTURE OF PHOTORECEPTIVE MEMBRANES OF DROSOPHILA COMPOUND EYES AS STUDIED BY QUICK-FREEZING ELECTRON-MICROSCOPY

Photoreceptive membranes of Drosophila compound eyes were studied by q uick-freezing electron microscopy. The quick-frozen photoreceptive mic rovilli appeared cylindrical in shape either when they were freeze-sub stituted or freeze-fractured. Deep-etch replication revealed the extra cellular surfaces of microvilli which were covered by various particle s arranged in a helical manner. The protoplasmic surfaces were covered by more regular helical rows of particles about 10 nm in diameter. Wh en rhodopsin content of the photoreceptive membranes was reduced by vi tamin A-deficiency, the intramembrane particles drastically decreased resulting in the disappearance of particles in rows. Our results stron gly suggest the regular arrangement of rhodopsin molecules in inverteb rate photoreceptive membranes.