 The life cycle of a jellyfish is similar in many ways to that of a coral or a dinoflagellate. The mature jellyfish is called the medusa, and that's what we recognize as a typical jellyfish that we encounter at the beach. The medusa floats around in the surface of the ocean and often reproduces extremely readily, releasing millions of eggs on a daily basis, often triggered by light levels. Once fertilized, these eggs form the planula stage and the planula continues to float in the oceans until it finds a suitable substrate to colonize, often concrete or rock. The polyp is the next stage, and this is the stage that colonizes the hard rock or the substrate, and this stage will continue to reproduce, this time asexually, forming new polyps. These polyps then continue to grow and often will bud to form colonies. Once conditions are right, often triggered by water, temperature, or nutrient levels, the polyp stage will then reproduce again asexually to form the new medusa stage, which will then grow into the mature jellyfish. Because jellyfish is so productive, both in the medusa stage and in the polyp stage, they are able to colonize massive areas with individuals, and this is the major threat of jellyfish, especially when overfishing in areas reduces their primary predator.