The effect of 5-fluorouracil on the development of the adult eye in Ephestia kühniella

The effects of the nucleic acid base analog, 5‐fluorouracil (5FU), on the development of the imaginal eye of the moth, Ephestia kühniella, were studied. Crystals of 5FU were implanted into the abdomina of pupae of known ages, and the extent of ommatidial differentiation occurring after this treatment was observed. In the study of normal development, it is observed that several early differentiation processes occur in a spreading fashion, i.e., a specific differentiation begins in the dorsoposterior region of the eye and spreads across the eye disc in a ventroanterior direction. All spreading processes are completed by 126–132 hours following pupation and all further differentiation occurs in all parts of the eye simultaneously. By 246–252 hours, all differentiation processes are essentially completed. Differentiation processes can be characterized by critical periods during which their occurrence can be completely inhibited by 5FU treatment. Those differentiations which are spreading processes can be further characterized by a period when 5FU treatment inhibits the progress of their spreading. Treatment at 78–84 hours no longer affects any spreading processes and, at 150–156 hours, it is no longer inhibitory toward complete ommatidial differntiation.