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Simple, yet complex

Probably the most familiar jellies are jellyfish, such as the Nausithoe punctata (above). Jellyfish are predators that use tentacles studded with stinging cells to catch and kill their prey, usually smaller zooplankton or fish. Although jellyfish have a very simple body structure, with no central nervous system, all have evolved efficient ways to catch their food. This species, for example, has symbiotic algae cells in its tissues that provide it with additional nutrition. A poster featuring this and several other open-ocean jellies is available at WHOI’s Ocean Science Exhibit Center.(Photo by Larry Madin, Woods Hole Oceanographic Institution)