At the bottom of the porpoise pool at Fjord&B\u00e6lt in Kerteminde, I filmed a quiet an interesting hunting.<\/p>\n\n\n\n
There was no hand, no teeth, no sudden strike. Just a sea anemone, fixed to the bottom like a small underwater flower, slowly eating a moon jellyfish, Aurelia<\/em> sp., much larger than itself.<\/p>\n\n\n\n Fjord&B\u00e6lt Aquarium<\/a><\/p>\n\n\n\n At first sight, the scene looked almost impossible. The jellyfish is the animal that could swim. The anemone is the one that could not go anywhere. Yet the free-swimming animal had become the prey of the sessile one. That is the first lesson of this small encounter: in the sea, being mobile does not always mean being safe.<\/p>\n\n\n\n Both animals belong to the same ancient animal phylum: Cnidaria<\/strong>. This group includes jellyfish, sea anemones, corals and hydroids. Cnidarians are famous for their specialised stinging cells, the cells that contain nematocysts<\/strong>: microscopic, pressurised capsules that can fire like tiny harpoons and are used for both prey capture and defence. So in this scene, predator and prey were not strangers. They were relatives, both armed with variations of the same cnidarian \u201chunting technology\u201d. But they use it in different bodies and lifestyles. The moon jellyfish represents the drifting, pulsating medusa form. The sea anemone represents the attached polyp-like predator: waiting, sensing, holding, digesting. This makes the encounter beautiful and slightly ironic: the animal we usually notice because it swims was caught by the animal that survives by waiting.<\/p>\n\n\n\n Sea anemones are often thought of as passive creatures, but they are predators. They catch small crustaceans, larvae, fish, organic particles and, in some documented cases, jellyfish. Scientists even have a word for eating jellyfish: medusivory<\/strong>. A jellyfish-eating sea anemone, Entacmaea medusivora<\/em>, was described from Jellyfish Lake in Palau feeding on the jellyfish Mastigias papua<\/em>.<\/a> Later observations recorded the same anemone feeding on several jellyfish species, including Aurelia aurita<\/em>. More recently, researchers reported the giant Caribbean sea anemone Condylactis gigantea<\/em> consuming moon jellyfish, Aurelia<\/em> sp., and upside-down jellyfish, Cassiopea<\/em> sp. That study also highlighted how natural-history observations, including public and citizen-science observations, can reveal interactions that are otherwise easy to miss.<\/p>\n\n\n\n