Candiru fish have a bit of a reputation. The tiny, wormy, nearly transparent catfish slide through murky Amazonian waters, wriggling their narrow heads into the gills of much larger fish. There, they latch on with strong teeth and guzzle blood like some kind of tick/glass noodle hybrid. The fish are perhaps most infamous for tales in which they are attracted to the urine of people peeing in the river and swim up their urethras, becoming horrifically embedded. (Hard evidence for this nightmare is more than a little dubious, and candiru don’t actually yearn for our pee.)