Fig. 4

Effects of light irradiance on retinal white-light sensitivity and rod and cone photoreceptor abundance. a White-light sensitivity of juvenile Megalops atlanticus maintained in ‘bright’ and ‘dim’ light conditions and tested by electroretinography (ERG). Average irradiances (µW s⁻¹ cm⁻²) required to elicit an 80 µV retinal response from fish held under each condition were significantly different between ambient illumination levels. Error bar obscured by the marker for fish in the ‘dim’ condition. b Relative rod and cone photoreceptor abundance in the retinas of fish held under ‘bright’ and ‘dim light conditions. Error bars indicate standard error of the mean