Chironex fleckeri

Chironex fleckeri, commonly known as the Australian box jelly and nicknamed the sea wasp, is a species of extremely venomous box jellyfish found in coastal waters from northern Australia and Papua New Guinea to Indonesia, East Timor, Cambodia, Malaysia, Singapore, the Philippines and Vietnam. It has been described as "the most lethal jellyfish in the world", with at least 64 known deaths in Australia from 1884 to 2021. Notorious for its sting, C. fleckeri has tentacles up to 3 m (10 ft) long covered with millions of cnidocytes which, on contact, release microscopic darts delivering an extremely powerful venom. Being stung commonly results in excruciating pain, and if the sting area is significant, an untreated victim may die in two to five minutes. The amount of venom in one animal is said to be enough to kill 60 adult humans.

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