Explorers in certain parts of the Amazon have to wear condoms if they are in the water because of a fish called the candirú. This fish is able – and willing in most cases – to swim into the human urethra as it is similar to the gills of the fish it usually attaches itself to. The candirú will then extend its needle-like spine and begin to feed off the blood of the host until it is removed by surgery!
In parts of India, live insects are often used as medicine. If you suffer from urine retention, a healer will gladly insert a Cimex lectularius – or bed bug – into your urethra, where it will siphon blood until the affliction is gone and probably beyond that too!
In secluded regions of the American northwest and Canada there lives a majestic bird with an curiously specialized beak. The brown-spotted peckerpecker has evolved the ability search for grubs inside the human urethra, where of course there are none, as some unfortunate loggers have found out. The peckerpecker was once endangered because of its foolish habits but as of 2005 they number in the thousands!
A deviously industrious species of crab is the Baja dick crab, named for its prevalence in the Baja region of California. The dick crab will spend weeks establishing a territory, but also expertly fashioning small hook-like objects out of calcium deposits and seaweed. Marine biologists were stupefied by this behavior until a hapless surfer wandered into dick crab country. An encroached-upon crab sprang into action and stealthily attached a hook to the victim's urethra, and then scuttled back down to fasten the rope-like fibers of the other end to a nearby stone. Seconds later there was a powerful scream and the beach bum was down. Further studies have shown that the dick crab does this in order to harvest puka beads from human necklaces or because it's a dick.
The Amorist squid, named for the late Dr. Amorist who discovered it, is truly the master of camouflage. On moonlit nights during the Amorist's mating season, which happens to be from February until August, the squid beaches itself on land near the seaports and dockyards of America and Europe's cities. Then, by positioning its tentacles just so, the Amorist can perfectly mimic the image of a high-class prostitute who's had a long night and is willing to give a suckjob for just ten dollars (eight Euro) if anyone's interested. Once a victim is ensnared, the Amorist wastes no time in filling the poor soul's urethra beyond capacity with eggs. Months later, young Amorists explode from the corpse's rotting kidneys and are put on welfare.