Color discrimination in the Atlantic Sand Fiddler Crab

Abstract

By Aaron Hamrick, biology

Advisor: John Layne

Presentation ID: CC_8

Abstract: Certain properties throughout the animal kingdom are experienced similarly such as size and shape however; color is not universally perceived the same for all organisms. Differences in number, type and sensitivity of cones in the visual system will determine the processing, discrimination and color perceived by the vision pathway. The amount of different cone types present in a visual system determines whether the organism is dichromatic or trichromatic. Most mammals and crustaceans are dichromatic, their cones sensitive to green and blue, while humans and few other species are trichromatic, sensitive to red/green/blue wavelength of light. Having the extra cone makes these organisms more sensitive to a wider range of wavelengths. This gives these organisms a greater complexity of color discrimination throughout a wider range of colors. We are interested particularly in the range of sensitivity of the visual system of the Atlantic sand fiddler crab, Uca pugilator. Uca pugilator was behaviorally tested to varying gray scale stimuli in the 470nm wavelength spectrum, a near blue color they see extremely well. These tests allow us to determine to what degree of discrimination this organism has visually in this wavelength. We chose this stimulus because it stimulates an inherent and natural response from subject in the form of eye tracking and keeps the signal output from the LEDs uniform, only altering the contrast. Preliminary results show consistency in sensitivity in line with the Weber Theory.