Behavioral Analysis of the Achromatic Discrimination Threshold in Phidippus Audax Jumping Spiders

Abstract

By Nuthara Jayasinghe, Biological Sciences - Animal Biology Concentration

Advisor: Nathan Morehouse

Award: Excellence in Research Communication

Presentation ID: 19

Abstract: Jumping spiders, or Salticidae, are known for their phenomenal vision and have been subject to many behavioral experiments based on tracking behavior which typically utilize high contrast stimuli to investigate jumping spider visual behavior. However there has been no behavioral evidence identifying the minimum contrast level that is sufficient for a spider to discriminate between two lights. This information would help us to understand how these spiders behave in realistic low light situations. Therefore, we are analyzing behavior to investigate the achromatic contrast threshold in Phidippus audax jumping spiders using a video playback paradigm paired with a trackball to measure behavioral responses. Our first objective was to optimize stimulus properties to maximize the reliability of response from the animal, by altering size, speed, and predictability of the stimulus path. This design was then used to test the achromatic contrast thresholds by varying the degree of achromatic contrast between the stimulus and the background. We investigated 15 different contrast levels between 24% and 0.026%. If the jumping spider can resolve the difference between the object and the background, it is expected to turn towards the object. We then use this rotational response to determine the contrast threshold at which a spider can no longer reliably discriminate between the two brightnesses. We expect that contrast levels lower than 5% will be difficult for the animal to resolve. Identifying the exact value of the threshold will then allow us to further investigate their visual capabilities with chromatic contrast experiments.