Figure 1.

Anatomy of an ommatidium of the female P. rapae crucivora in the main frontoventral part of the compound eye. Left, The schematic diagram shows that an ommatidium contains nine photoreceptor cells R1-R9 (1-9), with four distal photoreceptors, R1-R4, four proximal photoreceptors, R5-R8, and one basal photoreceptor, R9. The three transverse views are from the distal, proximal, and basal levels (dotted lines) of the ommatidium. The rhabdomeres, the photoreceptor organelles that contain the visual pigment, are joined into the fused rhabdom. The rhabdom is surrounded by four clusters of pigment that exist in the distal extension of the soma of the proximal photoreceptors. The bold arrow indicates the level at which the micrograph on the right was taken. Right, Depending on the ommatidium, the cluster pattern is a trapezoid (I), square (II), or rectangle (III). The pigment is pale red in ommatidial types I and III and deep red in type II. Spc, Secondary pigment cells that optically isolate the ommatidia. Scale bar, 10 μm.