To many, leeches are horrifying creatures. To a few, they're impressive and miraculous. They have 32 brains, 2 hearts, 300 teeth grouped in 3 jaws, five pairs of eyes... They latch and suck huge amounts of our blood, but they produce anesthetic and the most potent anticoagulant known, which are used in medicine when little vascular vessels need to be joint or repaired. And also for the production of drugs.

More information:

theguardian.com/10-stomachs-32-brains-a-day-inside-leech-farm