Jellyfish are simple, successful and, occasionally, deadly creatures. The Australian box jellyfish has enough toxin in each of its tentacles to kill 60 people. Some jellyfish create spectacular blooms when fields of polyps, their stationary life stage, simultaneously bud off into free-floating medusae. These blooms are blamed for the deaths of swimmers, clogged fishing nets and power plant intakes, and in certain parts of the world, like Japan, they appear to be on the rise.
But these problems are associated with only a subset of the creatures we call "jellyfish" – a catch all term for an amazingly diverse group of organisms. It includes corals, true jellies and others with stinging cells, as well as the stingless comb jellies, which swim using tiny hairs, called cilia.
What they also are is beautiful, as the following images attest.
Tropical-dwelling box jellyfish have a cube-shaped body, and four different types of special-purpose eyes: The most primitive set detects only light levels, but another is more sophisticated and can detect the color and size of objects. The Australian box jellyfish is also deadly; each of its up to 60 tentacles carries enough toxin to kill 60 people.
Mastigias jellyfish flood Jellyfish Lake, a marine lake in Palau, an island nation in the Pacific Ocean. Here, researchers found that pulsating jellyfish stir up the oceans with as much vigor as tides and winds, making them major players in ocean mixing.
Oldest Known Jellyfish Fossils
Jellies from Above
The moon jellyfish is common in many parts of the world, and it appears to have increased dramatically in Japanese waters in recent decades. Seen from a bird's eye view, a bloom of moon jellyfish appears as white swaths in a Japanese bay. In Japanese waters, its blooms have interfered with fishermen and power plants.
Blooms of Nomura's jellyfish have created serious problems in Japanese waters, including clogging fishing nets and stinging fishermen. Blooms have been recorded as far back as 1920, but they were rare events. But beginning in 2002, blooms have occurred nearly every year.