Masters Thesis

Investigating dermal behavioral responses in California red urchins

Recent research on sea urchins has shown that they possess unexpected visual capabilities. Behavioral tests have revealed that they are able to detect the spatial distribution and wavelength of light using the surface of their body. The well-studied purple urchin (Strongylocentrotus purpuratus) has a larger relative, the red urchin (Mesocentrotus franciscanus), which provides a number of advantages for studies in phototaxis. Light treatments used red, blue, and ultraviolet LEDs to illuminate one half of an urchin body. My results from red urchin trials agreed with published results from the purple urchin, indicating that both red and purple sea urchins show pronounced, significant negative phototaxis in the presence of blue light. My second study used targeted blue light beams as a probe to attempt to map red urchin responses on the geography of its body. To improve on previous published efforts, novel methods were designed to track an urchin during experimental trials, to analyze behavioral data, and reduce handling effects. Results indicate that a touch or chemical stimulus may confound the stimulus of blue light wavelengths, and that handling bias should be an important consideration in behavioral methods. Based on the results, a new detailed plan is presented for method modification to further research in this system.