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

Abstract

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.