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jellyfish : the typically free-swimming, bell-shaped, usually sexually-reproducing solitary or colonial form of a cnidarian in which the whorls of tentacles lined with nematocysts arise and hang down from the margin of the nearly transparent, gelatinous bell — Webster
Jellyfish or sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are not mobile, being anchored to the seabed by stalks. The bell can pulsate to provide propulsion and highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, the planula larva can disperse widely and is followed by a sedentary polyp phase.
Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the “true jellyfish”) are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast growing, mature within a few months and die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal group.
Jellyfish are used in research, where the green fluorescent protein, used by some species to cause bioluminescence, has been adapted as a fluorescent marker for genes inserted into other cells or organisms. The stinging cells used by jellyfish to subdue their prey can also injure humans. Many thousands of swimmers are stung every year, with effects ranging from mild discomfort to serious injury or even death; small box jellyfish are responsible for many of these deaths. When conditions are favourable, jellyfish can form vast swarms. These can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea. — Wikipedia
Palau’s Jellyfish Lake reopens as thousands of jellyfish return (Maggie Hiufu Wong, CNN)
Ongeim’l Tketau Jellyfish Lake – Open to Visitors (Palau Gov)
Jellyfish Lake, Eil Malk island, Palau (Wikipedia)
Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.
- Steep decline in giant sea turtles seen off US...on April 8, 2021 at 4:15 pm
Scientists were documenting stranded sea turtles on California's beaches nearly 40 years ago when they noticed that leatherbacks—massive sea turtles that date to the time of the dinosaurs—were among those washing up on shore. It was strange because the nearest known population of the giants was several thousand miles away in the waters of Central and South America.
- Human activities sound an alarm for sea lifeon April 6, 2021 at 3:08 pm
Humans have altered the ocean soundscape by drowning out natural noises relied upon by many marine animals, from shrimp to sharks.
- A mouse's bite holds venomous potential, finds...on March 29, 2021 at 7:00 pm
We are not venomous, and neither are mice—but within our genomes lurks that potential, suggest scientists from the Okinawa Institute of Science and Technology Graduate University (OIST) and the Australian National University. Reporting this week in PNAS, the researchers found that the genetic foundation required for oral venom to evolve is present in both reptiles and mammals.
- 'By-the-wind sailor' jellies wash ashore in...on March 18, 2021 at 3:55 pm
As their name suggests, by-the-wind sailor jellyfish know how to catch a breeze. Using a stiff, translucent sail propped an inch above the surface of the ocean, these teacup-sized organisms skim along the water dangling a fringe of delicate purple tentacles just below the surface to capture zooplankton and larval fish as they travel.
- Astronomers spot a 'space jellyfish' in Abell 2877on March 18, 2021 at 12:11 pm
A radio telescope located in outback Western Australia has observed a cosmic phenomenon with a striking resemblance to a jellyfish.