Illuminating camouflage: light-induced dopamine neurons help tadpoles disappear The balance between neurons expressing various neurotransmitters is thought to be set under genetic control during brain development. It’s a crucial step, enabling signalling among populations of neurons. A new study by Davide Dulcis and Nicholas Spitzer shows that natural stimuli can also regulate the class of transmitter expressed in the brain of postembryonic Xenopus tadpoles. Like endogenously dopaminergic neurons, neurons newly expressing dopamine drive a simple camouflage behaviour. The cover shows sibling tadpoles, one adapted to a dark background and the other to a white background. Natural light increases the number of dopaminergic neurons in the hypothalamus where this behaviour is controlled; dark exposure causes a decrease. This plasticity in the developing nervous system may have broad implications, and could be relevant to changes in cognitive states regulated by biogenic amines. Intriguingly, bright light therapy is used to treat patients with seasonal affective disorder, a type of depression linked to dysfunctional dopamine signalling. [Article p. 195; News & Views p. 177] (Cover photo: Norma Velazquez Ulloa, Armando de la Torre and Krista Todd.)