Semper Cells Research Articles

The compound eye in the opaque-eye phenotype of Drosophila 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 geometrical images.

Histology of the Compound Eye of Heliothis zea1,2,3

The ommatidium of the compound eye of the bollworm moth, Heliothis zea (Boddie), was found under a light microscope to be 660 μ long, 25 μ wide at the lens, and 7 μ wide at the basement membrane. It consists of a hexagonal lens resting on 4 crystalline cone cells (Semper Cells), each shaped like quadrants of a circle. The crystalline cone cells rest on the elongate crystalline cone. A spindle-shaped clump of 6–8 retinual cell nuclei is situated midway between the cone and the distal end of the rhabdom along the crystalline thread. Each crystalline thread and each retinula cell nuclei spindle is surrounded by the 6 pieces of the pie-shaped pigment envelope sections. The pigment envelopes extend from the cones to the distal end of the rhabdoms. Active pigment movement occurs within each envelope depending on the amount of light striking the ommatidium. The rhabdom is composed of 6—8 lobed rhabdomeres situated in the center of the hexagonal structure formed by the retinula cells. Each retinula cell appears to be served by a single axon. The axons leave the retinula cells, penetrate through a 10- to 12-μ layer of (highly reflective) tracheoles, spread apart, pass around a basal cell, and then converge to exit through the basement membrane as an axon bundle. The axon bundle converges with other bundles to form larger bundles which enter the optic ganglion. The cell walls of the basal cell are pigmented.

Histology of the Compound Eye of the Boll Weevil1,2,3

A histological study of the compound eye of the boll weevil, Anthonomus grandis Boheman, with a light microscope showed that each eye is composed of about 500 ommatidia 100–140 µ long, 27 µ in diameter at the lens, and 7 µ in diameter at the basement membrane. A single ommatidium consists of a hexagonal lens, a crystalline cone, 4 Semper cells, 2 primary pigment cells, 6 secondary pigment cells, 6 retinula cells which contribute to the formation of a central rhabdom that extends from the Semper cells to the basement membrane, and 2 basal pigment cells that surround the base of the retinula cells. The 6 axons, 1 from each of the 6 retinula cells, join and penetrate the basement membrane as a bundle. Each bundle of primary nerves converges with other bundles to form larger bundles that enter the optic ganglion.