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VM244: Diagnostic Methods for the Comprehensive Health Assessment of the Long-Spined Sea Urchin, Diadema antillarum

Figure 10. An urchin tries to seek shelter by moving into a dark box placed over its holding area. To increase the differentiation of light and dark areas, a bright light is pointed towards the urchin on the outside of the darkened space. A healthy urchin would move quickly into the dark, covered area.

Credit: R. Francis-Floyd, UF/IFAS