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Italy’s first record dates from 1946, in a tank at the University of Rome. The authors write that blooms are “irregular and unpredictable,” and most Italian reports fall between July and October.<\/p>\n\n\n\n
Stings too weak for human skin<\/h2>\n\n\n\n
According to the U.S. Geological Survey fact sheet<\/a>, the swimming form measures about 0.2 to 1 inch (5 to 25 millimeters) across. It is translucent, with a whitish or greenish tinge, and carries 50 to 500 tentacles.<\/p>\n\n\n\n Its stings can paralyze small invertebrates and tiny fish. A person is another matter: USGS says the stinging cells are “not likely to penetrate human skin,” and it lists the species as not dangerous.<\/p>\n\n\n\n It eats zooplankton, the small animals drifting in open water, and prefers larger, active prey such as copepods. Crayfish are the only predator of the bell stage that USGS considers important.<\/p>\n\n\n\n The bell, called a medusa, is the stage everybody photographs. USGS notes that the species more often exists in other forms. These include a dormant resting body, a crawling larva, a swimming larva and a polyp fixed to a hard surface.<\/p>\n\n\n\n The Italian paper puts the polyps at roughly 0.02 to 0.08 inch (0.5 to 2 millimeters), with no tentacles. Like the tiny jellyfish known for its reset trick<\/a>, this one switches between forms. Its polyps can bud off new polyps, crawling larvae or fresh bells.<\/p>\n\n\n\n Populations are often all male or all female, so new bells usually come from polyps. In Lake Santo of Monte Terlago, researchers found 16 females and one male in September 2023. That was only the second Italian population known with both sexes.<\/p>\n\n\n\n According to USGS, a single lake can go several years between blooms. Blooms are thought to need water of at least 77 degrees Fahrenheit (25 degrees Celsius). The polyp copes with colder water, and because it is so easy to overlook, its true range is hard to pin down.<\/p>\n\n\n\n How much the usual nets miss became clear in Switzerland in 2022. Researchers at the Swiss aquatic institute Eawag compared two survey methods with federal and university partners.<\/p>\n\n\n\n Standard kick nets, which catch animals stirred up from the riverbed, found no jellyfish at all. Environmental DNA, the genetic traces animals shed into water, found it in many Swiss river catchments.<\/p>\n\n\n\n “I would never have thought that this species would be so widespread,” Rosetta Blackman, then a postdoctoral researcher at Eawag, said in the institute’s announcement<\/a>. Eawag added that the nets still found more species overall, and project head Florian Altermatt of the University of Zurich said using both gives a more robust picture.<\/p>\n\n\n\n The species is believed to come from the Yangtze River basin. Yet scientists first described it in 1880, from a water lily tank in London’s Regent’s Park.<\/p>\n\n\n\n It has since reached every continent except Antarctica. It travels hidden in ornamental water plants, pet shipments and stocked fish. Plantings also steer other newcomers: in Catalonia, an ornamental street tree mattered at least as much as climate<\/a> for the giant resin bee.<\/p>\n\n\n\n In the United States, the USGS database lists records in more than 40 states. The earliest is from Kentucky in 1916. Kentucky, North Carolina, Ohio and Pennsylvania have all logged sightings in 2026.<\/p>\n\n\n\n Warmer water could widen its range. That was the finding of a 2021 study in Scientific Reports<\/a> led by Guillaume Marchessaux, then at the University of Palermo. His team projected suitable habitat expanding by 2050 and 2100 everywhere except Oceania, up into high latitudes in both hemispheres.<\/p>\n\n\n\n The same paper says heat is “necessary, but certainly not the only requirement” for a bloom. Its maps also use only sightings of bells, and the authors expect the polyps to be far more widespread.<\/p>\n\n\n\n The Italian authors stop short of calling this a spreading invasion. Sightings have risen considerably over the past ten years. But that jump may reflect more people looking and faster sharing of photos on iNaturalist and YouTube, they write.<\/p>\n\n\n\n They found no data to tell whether the range in Italy is “expanding, contracting, or stable.” They add that the bells are hard to detect because their short lifespan often gets in the way.<\/p>\n\n\n\n Eawag’s researchers have proposed DNA sampling as a complement to routine monitoring of invasive species. For swimmers, the bells are far smaller than the lion’s mane jellyfish found on Baltic beaches<\/a>, and USGS does not consider them dangerous.<\/p>\n\n\n\n The full study was published in Biology<\/a>.<\/p>\n\n\n\n Photo: CrazyBiker 84 \/ Wikimedia Commons, CC BY-SA 3.0<\/p>\n","protected":false},"excerpt":{"rendered":" A freshwater jellyfish from China, Craspedacusta sowerbii, has now been recorded at 61 sites across Italy. The list includes Lake … <\/p>\nFive forms of one animal<\/h2>\n\n\n\n
DNA traces in Swiss streams<\/h2>\n\n\n\n
Kentucky first, in 1916<\/h2>\n\n\n\n
More records, or more photos?<\/h2>\n\n\n\n