Figure 7. Lanthanum (La³⁺) mimics the trp phenotype in wild type fly but has no effect on a trp homologue mutant.

Intracellular recordings from single photoreptor cell of white-eyed Musca domestica (A) and from white-eyed nss mutant of Lucilia cuprina (Howard, 1984), which is a mutant homologue of the Drosophila trp (B). Responses to increasing intensities of orange lights are shown. The left columns show responses before application of La³⁺ (CONTROL). La³⁺ was applied by pressure injection into the extracellular space. Partial recovery of WT phenotype was observed 20 min after injection (A, right). Injection of La³⁺ to the extracellular space of the nss mutant had no effect on the rate of decline, but induced a small reduction in the amplitude of the initial peak response (from (Suss Toby et al., 1991)).