The fruit fly larva is typically photophobic: it does not like to be exposed to light and navigates to move away from the light source. For this behavior only one of the two photoreceptor types is required. The four blue-sensitive Rh5-photoreceptors are necessary for light avoidance, while the green-sensitive Rh6-photoreceptors are dispensable (Keene at al., 2011). A set of three neurons in the brain are further acting downstream or the larval eye to mediate light avoidance. While all three neurons belong to the clock circuit, only one neuron contacts the larval photoreceotor, the 5th-LN (Keene et al., 2011; Keene and Sprecher, 2012).
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Pauls D, von Essen A, Lyutova R, van Giesen L, Rosner R, Wegner C, Sprecher SG Potency of transgenic effectors for neurogenetic manipulations in Drosophila larvae Genetics, 2015 Jan;199(1):25-37
Kane EA, Gershow M, Afonso B, Larderet I, Klein M, Carter AR, de Bivort BL, Sprecher SG, Samuel AD.
Sensorimotor structure of Drosophila larva phototaxis.
Proc Natl Acad Sci U S A. 2013 Sep 16.
Keene AC, Mazzoni EO, Zhen J, Younger MA, Yamaguchi S, Blau J, Desplan C and Sprecher SG Distinct visual pathways mediate Drosophila larval light avoidance and circadian clock entrainment. J NEUROSCI. 2011 Apr 27;31(17):6527-34.
Diaz NN and Sprecher SG Photoreceptors: Unconventional ways of seeing. CURR BIOL. 2011 Jan 11;21 (1):R25-7
Keene AC and Sprecher SG. Seeing the light: photobehavior in fruit fly larvae, Trends Neurosci. 2012 Feb;35(2):104-10