Light pulses at night elicit wavelength‐dependent behavioral responses in zebrafish

Zebrafish detect and respond to light by means of visual and non‐visual photopigments that have maximal sensitivity at different wavelengths. This paper describes zebrafish behavior when a 1‐h light pulse of different wavelengths (violet, blue, green, orange and red) was applied at midnight, with light pulse and darkness being used as controls. For each light condition, seven fish were individually tracked 1 h before ( P 1), during ( P 2) and after ( P 3) the light pulse. All the light colors (except orange) led to an increase in the accumulated distance swum during P 2 with respect to the baseline ( P 1) activity, but only the white, violet, blue and green pulses led to higher activity during P 3. This activation was partially explained by changes in the maximum swimming speed and/or the freezing behavior time. Thus, the violet and green lights increased the maximum swimming speed during P 2, whereas red light produced a decrease in the same in P 3. The white and blue pulses elicited longer freezing behavior during P 2 than the violet pulse, and only the white and blue lights provoked freezing behavior during P 3. Similarly, all colors awakened fish during P 2, but only the green, blue, violet and white light affected the sleep rebound during P 3. Moreover, zebrafish swam downward only during the white and violet light pulses in P 2. Summarizing, shorter wavelengths strongly affected zebrafish behavior, especially after exposure (except for the vertical location). The persistence and magnitude of the effects on zebrafish behavior elicited by different light colors could suggest that dissimilar internal signals of phototransduction are activated by different wavelengths.