Pupil Control in Compound Eyes: More Than One Mechanism in Moths

In many arthropod compound eyes, migrating granules of screening pigment serve as a light-regulating pupil. Mobile pigments are found both in the photoreceptor cells and in specialized pigment cells. Recently there have been several conflicting reports on how the migrations in the pigment cells are controlled in the eyes of moths. Some investigations indicate that the pigment cells are controlled by the receptor cells (White et al., 1983; Bernard et al., 1984; Weyrauther, 1986), whereas other investigations show clearly that the pigment cells are independent and triggered by a light sensitivity of their own (Hamdorf et al., 1986; Land, 1987). We here present evidence for two coexisting mechanisms that control migrations in the pigment cells of some moths. Depending on the experimental design one of these mechanisms may take preference over the other, thus explaining the previous contradictory results.