By Dr. Rob Neumann
Select Science—An article published in Current Zoology sheds new light as well as confirms some previous findings on largemouth bass vision.* The study focused on the visual system and visual perception of color in largemouth bass and involved three research components: determine the number and spectral sensitivity of photoreceptors in the eye; model visual perception; and test color perception using behavioral experiments. The study utilized both northern and Florida subspecies of largemouth bass, so the question of whether there were differences in photoreceptor sensitivities between the two subspecies was also addressed.
The northern and Florida bass tested showed similar visual sensitivities. Results confirmed a dichromatic visual system with green-sensitive single cone cells and red-sensitive twin cone cells, in addition to rod cells. Vision models indicated that the bass’ dichromatic vision limits the perception of yellow coloration, so chartreuse yellow should appear similar to white. The authors explain this happens because chartreuse yellow equally stimulates both the green and red cone cells at similar frequencies. Behavioral tests, which used sets of training colors in various configurations in combination with food stimuli dispensed from a specific test color, confirmed model predictions that chartreuse yellow is indistinguishable from white.
Their models also predicted blue, green, and black would appear similar to bass, and behavioral tests partially supported this prediction. Bass trained to blue frequently struck at black, and vice versa, thus black and blue were indistinguishable. Similar to findings in another study, bass could discern green from black and grays, but had difficulty discerning green from blue, according to their model.
In the largemouth bass system, chromatic cues (of relating to hue) are easier to identify, the researchers say. Bass could readily identify red and green and could distinguish these colors from achromatic alternatives (shades of black and gray, which lack hue but were of similar brightness to red and green). Bass, however, had difficulty associating “meaning” to achromatic cues (white, black, and for bass, yellow).
*Mitchem, L. D., S. Stanis. M. Zhou, E. Loew, J. M. Epifanio, and R. C. Fuller. 2019. Seeing red: color vision in largemouth bass. Current Zool. 65(1):43-52.