What is the stimulus response of the sea urchin?

The stimulus response of a sea urchin involves a range of behaviors triggered by environmental stimuli. For instance, when exposed to light, sea urchins may exhibit negative phototaxis, moving away from bright light sources. They also respond to chemical stimuli in the water, such as food or toxins, by adjusting their movement or retracting their spines. Additionally, sea urchins can display defensive behaviors in response to predators, including curling up and using their spines for protection.