Turns with multiple and single head cast mediate Drosophila larval light avoidance

PLoS One. 2017 Jul 11;12(7):e0181193. doi: 10.1371/journal.pone.0181193. eCollection 2017.

Abstract

Drosophila larvae exhibit klinotaxis when placed in a gradient of temperature, chemicals, or light. The larva samples environmental stimuli by casting its head from side to side. By comparing the results of two consecutive samples, it decides the direction of movement, appearing as a turn proceeded by one or more head casts. Here by analyzing larval behavior in a light-spot-based phototaxis assay, we showed that, in addition to turns with a single cast (1-cast), turns with multiple head casts (n-cast) helped to improve the success of light avoidance. Upon entering the light spot, the probability of escape from light after the first head cast was only ~30%. As the number of head casts increased, the chance of successful light avoidance increased and the overall chance of escaping from light increased to >70%. The amplitudes of first head casts that failed in light avoidance were significantly smaller in n-cast turns than those in 1-cast events, indicating that n-cast turns might be planned before completion of the first head cast. In n-casts, the amplitude of the second head cast was generally larger than that of the first head cast, suggesting that larvae tried harder in later attempts to improve the efficacy of light avoidance. We propose that both 1-cast turns and n-cast turns contribute to successful larval light avoidance, and both can be initiated at the first head cast.

MeSH terms

  • Animals
  • Behavior, Animal / radiation effects
  • Drosophila / physiology*
  • Drosophila / radiation effects
  • Larva / physiology
  • Larva / radiation effects
  • Light*
  • Phototaxis / physiology

Grants and funding

This work was supported by grants from the National Basic Research Program of China (973 Program 2013CB945603),the National Natural Science Foundation of China (31070944, 31271147, 31471063, 31671074, and 61572433), and the Natural Science Foundation of Zhejiang Province (LR13C090001 and LZ14F020002).