Effect of Neurotransmitters on Movement of Screening Pigment in Insect Superposition Eyes

Com pound Eye, Pigment Migration, Adrenaline, Octopamine, Noradrenaline The light-induced expansion of the screening pigment in the com pound eyes of the sphingid moth Deilephila and the owlfly Ascalaphus is counteracted by local application of noradrenaline or octopamine. Ata critical concentration, similar for both drugs, the expanding effect caused by a light stimulus is completely neutralized, and at higher drug concentrations light stimulation induces a contraction of the screening pigment. The contracting effect of noradrenaline and octopamine is counteracted by adrenaline. None of the other putative neuroactive substances tested (acetylcholine, GABA , histamine, melatonin, serotonin and taurine) has a com parable effect on light-induced pigment movement. It is hypothesized that pigment migration is controlled by a system of antagonistically acting catecholamines, similar to the noradrenaline/adrenaline system present in vertebrates.