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The original was posted on /r/todayilearned by /u/iamveryDerp on 2023-08-06 23:57:13+00:00.

Original Title: TIL about an Australian jellyfish that causes Irukandji syndrome: excruciating muscle cramps, severe pain in the back and kidneys, a burning sensation of the skin and face, headaches, nausea, restlessness, sweating, vomiting, and psychological phenomena such as the feeling of impending doom.