Date of Award
Spring 2026
Document Type
Open Access Dissertation
Department
Biological Sciences
First Advisor
Daniel I. Speiser
Abstract
It is crucial that animals are able to perceive visual contrast for a variety of tasks including gaze stabilization, object detection and navigation. In some light environments it can be challenging for an animal to perceive visual contrast. For example, the visual scene in tidal creeks can be spectrally narrow and have high levels of caustic flicker, which respectively lower chromatic and achromatic visual contrast. Additionally, the visual conditions of tidal creeks can change drastically over time due to local conditions such as algal blooms and weather. Animals can take different approaches to enhancing their perception of visual contrast depending on the light available in their environment. Since tidal creeks are so dynamic, animals may need to employ more than more strategy to reliably distinguish cues. My aim was to determine how tidal creek crustacean vision may be suited to tidal creeks.
To investigate vision in tidal creeks I used two crabs commonly found on the coast of South Carolina: the Atlantic mud crab, Panopeus herbstii and the green porcelain crab, Petrolisthes armatus. I hypothesized that the visual systems of these crabs may have increased light sensitivity, use chromatic or polarized cues or all of the above to enhance their perception of visual contrast. To investigate crab vision, I used a combination of behavioral and physiological experiments. I found neither species used the angle of linear polarization (AoLP) to stabilize their gaze but they did exhibit cardiac responses to looming stimuli that varied in AoLP. I found that the reflecting superposition eyes of porcelain crabs out-performed the apposition eyes of the mud crabs by having faster vision, a wider dynamic range and two classes of photoreceptor whereas mud crabs have one. Lastly, compared to mud crabs, porcelain crabs responded more frequently to looming objects with low Weber contrasts, suggesting that they have higher contrast sensitivity.
My findings suggest porcelain crabs enhance their perception of visual contrast in tidal creeks using high irradiance sensitivity, chromatic cues, and perhaps AoLP. My evidence shows mud crabs may use low contrast achromatic cues and AoLP to enhance contrast. For animals that inhabit visually noisy environments it is likely crucial for crabs to enhance visual contrast so that they can visually detect predators and prey in visually noisy scenes.
Rights
© 2026, Madison M. Janakis
Recommended Citation
Janakis, M. M.(2026). The Visual Ecology of Tidal Creek Crabs. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/8837