Increasing DHS1P induces Sk1-expressing photoreceptors to degenerate, and photoreceptor degeneration in Sk2 overexpressors is suppressed in a CalX mutant. (A) Photoreceptors of Sk1 overexpressors degenerate when DHS1P is increased. In DHS1P-fed Sk1 flies, 32% of the rhabdomeres are intact compared with flies raised in solvent. (B) Photoreceptor degeneration in 7-d-old Sk2 overexpressors is suppressed in a calx^B mutant, suggesting altered calcium homeostasis is a likely cause of degeneration. 81% of the rhabdomeres are intact in Sk2 overexpressors in calx^B; however, many rhabdomeres are elongated in shape.