Cuticle sclerotization precursor N-β-alanyldopamine also plays a role in the regulation of larval phototactic behaviour in Drosophila melanogaster (Diptera: Drosophilidae)

Phototaxis is a well-studied insect behaviour described as rigid and stereotyped. Larval response to light can be assessed by a fast and highly repetitive assay like a half-dark/half-illuminated plate. Drosophila melanogaster Meigen (Diptera: Drosophilidae) mutants can be used to study the response of larvae to sensory stimuli. Adults of the ebony mutant show behavioural deficits such as abnormal circadian rhythms and severe defects in vision, whereas the tan mutants show a slight deficiency in vision. We analysed the response of D. melanogaster mutant larvae for N-β-alanyl derivatives metabolism (ebony and tan) to determine whether they also show abnormal phototactic behaviour. Our results showed that ebony larvae exhibited a random response to light, whereas tan larvae showed a similar response to wild-type larvae. To assess if N-β-alanyl derivatives metabolism might be involved in the response of larvae to light, we fed them with N-β-alanyldopamine (NBAD), N-β-alanylhistamine (carcinine) or dopamine. NBAD restored the wt response in ebony larvae, whereas carcinine and DA produced no effect. These results suggest, for the first time, that NBAD might act as a neuroactive compound involved in the phototactic response of the D. melanogaster larvae.