A deadly species of jellyfish, translucent and the size of a thumbnail, is spreading along Australia’s coastline as a result of global warming, scientists warned today. Irukandji jellyfish are among the world’s most toxic creatures – all but impossible to detect in the water but packing a potentially lethal punch belying their tiny size. Until recently it was thought that they were confined to Australia’s northern tropical waters, but marine biologists have now found them off Queensland’s Fraser Island — a popular tourist spot about 400 miles south of their previously assumed range. Their discovery has halted production of a Hollywood film, Fool’s Gold, starring Kate Hudson and Matthew McConaughey, who were originally due to be filmed swimming in the sea. Dr Jamie Seymour, from James Cook University, said she had found five of the animals off the island. “You can’t now say the waters around Fraser Island are jellyfish safe. I mean, these animals have the potential to kill you,” he told ABC radio. “The ones we were catching weren’t any bigger than your thumbnail. They’ve got tentacles that are probably a half to three quarters of a metre long, and pretty much transparent. So unless you really know what you’re looking for, you’re not going to see them in the water.” If they migrate south in sufficient numbers, irukandji would threaten the safety of swimmers, surfers and snorkellers along southern Queensland’s Gold Coast and Sunshine Coast holiday destinations. Little is known about their biology but their toxicity is legendary. One of the tiny jellyfish was blamed for killing a 58-year-old British tourist, Richard Jordan, in the Whitsunday Islands of Queensland in 2002. A few months later, a 44-year-old American tourist was stung and also died.