The ecological niche of jellyfish has remained largely unchanged for more than 600 million years. Jellyfish are carnivorous and live on plankton, small crustaceans, fish eggs, fish and other jellyfish. In turn, they are preyed on by tuna, sharks, sea turtles, swordfish and salmon.
Some regions, such as the Caribbean and Hawaii, experience incursions of invasive jellyfish species with few or no natural predators. Jellyfish use their tentacles as drift nets to capture food. When fish or other creatures make contact with the tentacles, the tentacles respond by firing paralyzing toxins into the prey. The jellyfish then uses its tentacles and smaller growths known as oral arms to move the paralyzed prey to its mouth.