Sea urchin Sea urchins have incredibly long lives, living 50 to100 years. They reproduce early and prolifically, releasing several million eggs at a time. They are very vulnerable to predation when they are young and small. Once they reach adulthood, however, predators, other than man and sea otters, take less interest, probably because their spines become more threatening as they grow. The name “urchin” is an old word for hedgehog, which sea urchins resemble. Uni is considered an aphrodisiac in Japan.