Purple Urchin

Purple sea urchins prefer to eat kelp. They have 2 different feeding modes: they can act as sedentary feeders catching drifting kelp, but when this supply drops off, they switch to active foraging and can form dense feeding fronts that completely remove a kelp forest, leaving behind an urchin barren. Once the forest/food is gone, the gonads of the urchin shrink, so they lose their nutritional value for any potential predators, and may exist in this zombie state for decades. A decrease in the predators of urchins, especially sea otters and sunflower stars, has enabled them to overpopulate.

Sea otters, sunflower stars, leather stars, California sheepshead, spiny lobsters, and white sea urchins are their main predators.

Purple sea urchins have been extensively used in scientific research, including in developmental biology studies, since they have clear embryos.