A laboratory study of the correlation between texture and the speed of locomotion by the sea urchin Hemicentrotus pulcherrimus

This laboratory study examined the relationship between substrate texture and movement speed of the sea urchin Hemicentrotus pulcherrimus. We assessed the movement speed of 14 sea urchins placed on either acrylic, or three types of waterproof sandpaper, on the bottom of a water tank. Images were taken at regular intervals and analyzed to determine the speed of each sea urchin. Light intensity was stronger at one end of the tank. Our analysis showed sea urchins moved away from light, at a speed that was negatively correlated with the roughness of the substrate, with slower movement on rougher surfaces. This result has implications for the design of equipment for capturing sea urchins in areas where their explosive population growth presents a threat to algal growth and reef environments.