Dark Banquet - Bill Schutt [96]
One major problem that all vampires must overcome is hemostasis, or blood clotting. This process actually consists of a maddeningly complex cascade of chemical reactions that must occur before a clot forms.*153 For the creature carrying around all that blood, the key benefit to this hemostatic complexity is that it prevents blood from clotting where and when it shouldn’t. The downside to the clotting cascade is that it has enabled blood feeders to interfere with the clotting process at multiple points along the chemical pathway. In other words, if there were only one step in the clotting process where the potential blood feeder could thwart the process, the odds of evolving that ability would be pretty low. But if blood clotting can be disrupted at any one of many points in a complex chemical cascade, the odds would be much higher that such a clot-disrupting substance would evolve. As a result, although each vampire has its own separately evolved anticlotting substances, the outcome is identical—freely flowing blood from the prey, with clot formation delayed until after (sometimes long after) a blood meal has been obtained.
Considering how long their “manufacturers” have been in business, these natural anticoagulants are often far more efficient than anything produced by man, and several of them have become important medications. For example, the clot-dissolving properties of the vampire bat–derived substance desmokinase have been used to combat strokes, while hirudin, an anticoagulant found in leech saliva, is used to prevent blood clots from forming after hip replacement surgery. Additional vampire-derived compounds (like anesthetics, perhaps) have tremendous potential for use in the field of medicine and we can certainly expect to hear more about them as researchers explore the field.
But besides a potential for providing us with some useful pharmacological products, do blood feeders provide any additional benefits?
The answer is most certainly yes.
Vampire bats remain great examples for learning about the pitfalls of scientific discovery, especially how problems can arise when prejudice and misinterpretation substitute for careful observation and experimentation. Unfortunately, some of these early errors have perpetuated a slew of misconceptions about bats (although the next time someone implies that most bats are blood feeders, you’ll be ready to pounce). Each year, thousands upon thousands of beneficial bats are killed because of fear and ignorance, and the problems that do exist with vampire bats (generally, Desmodus) are actually the result of man’s destruction of the natural environment, combined with our dogged insistence on propagating domestic animals in places where they just don’t belong. Desmodus and its cousins, Diaemus and Diphylla, display an amazing array of adaptations for their blood-feeding lifestyles and as such they are poor representatives for bats as a group. Far more typically, bats help reduce the number of harmful insects, pollinate plants that are essential to their ecosystems (and to humans), and help to reforest tropical regions shattered by slash-and-burn agriculture.
On another very important level, sanguivores provide food for a variety of other creatures. Leeches, for example, are a preferred meal of many species of freshwater fishes, a fact hasn’t gone unnoticed by the fishing bait industry (one company offers a discount for leech orders over twenty-five pounds). Fishermen use leeches to catch game fish such as walleye (Sander vitreus), smallmouth bass (Micropterus dolomieu), and northern pike (Esox lucius), as well as smaller pan fish like bluegills (Lepomis macrochirus). Mosquitoes are another important food source, especially for birds and bats.*154 Mites, ticks, and chiggers are also eaten,