Others include mosquitoes, ticks, vampire bats , bed bugs, lice, other insects and the lamprey fish. All these feed on larger animals – but don’t kill them, so they are all called parasites. In nature, the medicinal leech inhabits the wetter environments of western and southern Europe. Sensing the warmth, motion, or shadow of possible prey, the leech cozies up, attaches itself with its suckers, injects an anesthetic so that its presence is not detected, and goes to work. The three jaws of its head sucker stiffen, protrude, and slice into the prey’s skin with a sawing motion.
Immature leeches feed on the thin-skinned bodies of amphibians and young fish; mature leeches can move on to larger prey, such as cattle, horses, ducks, and humans. The leech’s natural anticoagulant, hirudin, keeps blood flowing for the 20 to 40 minutes it takes to feed, during which time the leech’s body weight may increase 10 times, reaching up to 60 grams . The secretions of one leech can prevent up to half a cup of blood from coagulating.
The exhibition, called “Bloodsuckers,” includes displays of other live animals—mosquitoes, ticks and leeches—interspersed throughout the gallery. And dozens of preserved specimens, arrayed down a long, curving wall, offer a glimpse into the diverse world of the roughly 30,000 species of bloodthirsty organisms across the globe. Among these critters are vampire moths, which can pierce the thick skins of buffalo and elephants. Vampire snails target sick and dying fish, making for easier prey. The oxpecker birds of Africa pluck ticks and other insects off large mammals—and then slurp blood from their hosts’ sores. Leeches are not the only animal that feeds on the blood of animals.
Blood sucked into its crop can take 18 months to digest. During this time, the leech does little but lie around in a stupor, rousing itself only to reproduce. The hermaphroditic leech copulates on land, wrapping around its partner using a kind of mucus, and later secretes a cocoon, which it deposits in damp soil near the shoreline. Within two to four weeks, about 15 to 25 leeches hatch. Under the right conditions, a leech can produce up to 1,200 young in a five-year lifetime.
At Biopharm, leeches feed on pig blood poured into an artificial membrane that simulates the skin of natural prey. After rearing the leeches for six months at 80 degrees Fahrenheit, Peters transfers them to a room chilled to a growth-slowing 45 degrees. When leeches leave Biopharm—thousands a year—they are packed like Chinese takeout in little cardboard boxes. They go to such places as Carolina Biological Supply, in Burlington, North Carolina, where workers store them in buckets of icy spring water until a surgeon like Levin calls. “We maintain them so that when surgeons get one, it’s a nice, clean, hungry leech,” says Lawrence Wallace, the firm’s director for live biological products. In the gut of every one, even those raised in sterile conditions, livesAeromonas hydrophila,a bacterium that prevents putrefaction of the leech’s blood meal and supplies enzymes crucial to its digestion.