Effects of light environment during growth on the expression of cone opsin genes and behavioral spectral sensitivities in guppies (Poecilia reticulata)

Abstract

Background: The visual system is important for animals for mate choice, food acquisition, and predator avoidance. Animals possessing a visual system can sense particular wavelengths of light emanating from objects and their surroundings and perceive their environments by processing information contained in these visual perceptions of light. Visual perception in individuals varies with the absorption spectra of visual pigments and the expression levels of opsin genes, which may be altered according to the light environments. However, which light environments and the mechanism by which they change opsin expression profiles and whether these changes in opsin gene expression can affect light sensitivities are largely unknown. This study determined whether the light environment during growth induced plastic changes in opsin gene expression and behavioral sensitivity to particular wavelengths of light in guppies (Poecilia reticulata).

Results: Individuals grown under orange light exhibited a higher expression of long wavelength-sensitive (LWS) opsin genes and a higher sensitivity to 600-nm light than those grown under green light. In addition, we confirmed that variations in the expression levels of LWS opsin genes were related to the behavioral sensitivities to long wavelengths of light.

Conclusions: The light environment during the growth stage alters the expression levels of LWS opsin genes and behavioral sensitivities to long wavelengths of light in guppies. The plastically enhanced sensitivity to background light due to changes in opsin gene expression can enhance the detection and visibility of predators and foods, thereby affecting survival. Moreover, changes in sensitivities to orange light may lead to changes in the discrimination of orange/red colors of male guppies and might alter female preferences for male color patterns.

Keywords: Color vision; Light environment; Opsin; Sensory drive; Sexual signals.

Fig. 1

Behavioral sensitivities to the stimulus wavelengths of light of individuals grown under green light (N = 5) and those grown under orange light (N = 5) at various wavelengths. The behavioral sensitivity was calculated as the negative logarithm of threshold detectable light intensities (μmol/m²/s) according to optomotor responses (see Methods section). Circles indicate the means ± standard errors of the mean (SEM)

Fig. 2

The mean (± standard errors of the mean (SEM)) expression values of cone opsin genes relative to housekeeping genes according to separate quantitative polymerase chain reaction (qPCR) experiments for individuals grown under green light (Green, N = 8) and those under orange light (Orange, N = 6). Gene expression values of cone opsins were normalized to the geometric mean value of the expression of housekeeping genes

Fig. 3

The relationship between the principle component 3 (PC3) and the behavioral sensitivity to 600-nm light. The gene expressions of long-wavelength-sensitive (LWS)-1 and -3 positively contribute to PC3 values (see text and Additional file 1: Table S4). The values of behavioral sensitivity were the negative logarithm of threshold detectable light intensities