Figure 1.

Morphology of degenerating norpA cells. Flies were reared at room temperature under constant light. A, The norpA⁺ retina shows the normal position of a photoreceptor (white arrow). The photoreceptor contains a well organized rhabdomere (R) and has adherens junctions (aj) connecting neighboring photoreceptor cells. The pigment cells (black arrows) possess a homogeneous granular cytoplasm and are located on the basal side of the photoreceptor cell opposite the rhabdomere. B, The 1-d-old norpA photoreceptors, at initial stages of degeneration, possess smaller, less organized, rhabdomeres and condensed cytoplasm. The pigment cell (black arrow) has expanded and begins to surround the photoreceptor as it loses contact with neighboring phototoreceptors. C, D, At 2 d, many photoreceptors (white arrows) are completely engulfed by an enlarged pigment cell. The photoreceptors become filled with vesicles and vacuoles, and the rhabdomeres are further disintegrated. Scale bars, ∼5 μm.