A small hydroid found aro und the world. It is usually innocuous, but in one small area of the northern Honshu island of Japan, and in a similar area on the opposite side of the Sea of Japan around Vladivostock, a sting causes severe systemic symptoms very similar to the Irukandji syndrome. Similar to Irukandji stings, Gonionemus stings occur in epidemics with more in some years than others. It has not caused a proven death, although some unproven deaths have been claimed in the past.
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