The compound eye in the opaque-eye phenotype of Drosophilia melanogaster

The compound eye of the opaque-eye mutant of Drosophila melanogaster was investigated by means of electron microscopy to determine the morphological and physical properties of ommatidial elements. These elements in the mutant were found to differ from those of the wild-type flies in the following ways: (1) The cuticular lens was thinner than that of the control and lacked the typical lamellar construction. (2) The Semper cells were irregular in shape and contained many membranous inclusions similar to those found in degenerating cells; also their nuclei contained virus-like particles. (3) The primary pigment cells contained an abundance of drosopterin-containing granules which were lacking in those of wild-type flies. (4) The superior and inferior central photoreceptor cells were misplaced and their rhabdomeres evidenced some degeneration. (5) The secondary pigment cells had only one type of pigment granules instead of the three types found in the control. These morphological changes in ommatidial elements induced physical abnormalities such as the apparent opaqueness of the eye, the lack of a pseudopupil, the probable disability of the photoreceptor cells to respond to light and the inability of the dioptric system to produce utilizable geometric images.