The Skillful Leech
By Tamia Nelson
August 26, 2008
Six of us in four boats headed out across a marsh in northern Québec, on our way to the lake at the head of the river that we all planned to run. But first we had to find the elusive channel linking the marsh and the lake. It wasn’t easy. To begin with, we followed several false leads, paddling down a succession of seemingly endless labyrinths, only to have each one end in a boggy cul-de-sac. At long last, though, we found what we were looking for. But our troubles weren’t over. The channel dwindled away to a shallow trickle. We could see our destination just ahead, but to get to it we had to leave our heavily loaded canoes and wade.
Clouds of muck rose from the bottom as we clambered gingerly over the gunwales of our boats. Soon we were shuffling forward, calf-deep in a semi-liquid ooze that looked like the dregs you’d find at the bottom of an old-fashioned percolator. Our slog didn’t last long. Only minutes later, we were seated on boulders scattered along the lakeshore, and the first thing we did was strip off our soaking-wet sneakers and socks.
That’s when Kathy screamed.
Not stopping to put our sneakers back on, the rest of us hobbled over to see what was wrong. Kathy was seated on a good-sized rock, a muddy sock clutched in one hand while she gestured frantically in the general direction of her newly exposed foot with the other. And clinging to her foot’s sodden white flesh was…you’ve probably guessed it…a brace of leeches. One nestled in the hollow just below her ankle bone. The other hung from her big toe. It was obvious that Kathy’s screams hadn’t distracted the two leeches from the task in hand. They continued to enjoy a meal at her expense, their chubby bodies pulsing contentedly. As luck would have it, Kathy was a convivial gal, and invitations to her dinner parties were much sought after. On this occasion, however, her social graces deserted her completely. That day in Québec, she wasn’t at all happy to be playing the part of hostess. Her screaming continued for some time.
I don’t need to explain why, I’m sure. You won’t see many wildlife calendars featuring glossy photos of leeches. Wolves, loons, and whales get folks reaching for their wallets in seconds, but leeches only inspire a shudder of revulsion. OK. Call me contrary, if you want, but I actually like leeches. I suppose I admire their “exquisite efficiency.” (The words belong to Professor Ann Haven Morgan, whose Field Book of Ponds and Streams is an old friend.) In any event, I’m not alone. Physicians are rediscovering their value, too. In 2004, the US Food and Drug Administration formally granted Hirudo medicinalis (aka the medicinal leech) recognition as a “medical device.” I don’t care much for the “device” bit, I admit, but the FDA’s belated acknowledgment is only right and proper. After all, back in the days when bleeding was pretty much the gold standard of treatment for a whole host of ailments and afflictions, ranging from gout to madness, physicians themselves were often referred to as leeches, so closely were they identified with these tools of their trade. Now things are coming round full circle. Leeches are back in the doctor’s little black bag of tricks, full-fledged professional partners in a host of cutting-edge microsurgical and reconstructive procedures—anywhere, in fact, where venous congestion threatens tissue survival. As Kathy can attest, leeches are experts at getting blood flowing.
But my interest in—indeed, my affection for—leeches isn’t grounded in their therapeutic potential. I just find them elegant swimmers, superbly adapted to their watery home. Moreover, they’re…
An Extensive Tribe
Their kindred numbers more than 700 species in all. Some even live on land, though many more are aquatic. And—Kathy may take some comfort in this—most are not out for our blood, at least not when they have any choice in the matter. Leeches are actually quite finicky eaters, as choosy about the provenance of their meals as any wine snob is about the appellations and vintages on the bottles in his cellar. For instance, some leeches prefer turtle blood, while others favor the blood of fish or snails, and still others eschew blood altogether, subsisting entirely on small invertebrates.
That said, leeches, too, are invertebrates. They’re annelids, or segmented worms, distant cousins to the common earthworm, that familiar sight in gardens and bait pails, as well as a frequent ornament on sidewalks following heavy rains. (Theirs is not a particularly close-knit family, it must be said. One species of leech even feeds on earthworms. So much for family ties.) You can tell a lot about a leech just by looking at it. A hungry leech is lean, with the flat stomach of a body-builder, while a well-fed leech is as rotund as any stage Falstaff. (A feeding leech can swell to ten times its original size, so distensible is its architecture. Falstaff would be envious, though his envy might abate somewhat on learning that a leech may go for more than a year between meals.) Lacking hands, paws, or claws, leeches make do with suckers at each end of their bodies. The hind sucker is just a holdfast, but in leeches that feed on blood the oral sucker is part of a very efficient extraction apparatus.
This is a good time to consider just how it was that Kathy could play unwitting hostess to two blood-sucking leeches without knowing it—until she took off her sneakers, that is. The secret lies in the leech’s superbly efficient surgical technique. His tiny teeth are wonderfully sharp, and he releases a local anesthetic into his victim’s flesh. (I say “his,” but I could just as easily have written “hers,” and with no less accuracy. Leeches are true hermaphrodites, bundling the reproductive machinery of both sexes together in one package.) As a result, the wound is almost always painless. It may itch later, however, especially if a feeding leech is removed early in the course of his meal. This is because he also injects hirudin, a powerful irritant and anticoagulant. If he’s allowed to finish eating, most of this irritating substance will be sucked out, but if a leech is interrupted while at table, he’ll leave an unwanted present behind for his hostess. In either case, the wound may continue to ooze blood for some time, though in the absence of a pre-existing clotting disorder the resulting blood loss is usually slight.
Once he’s fed to repletion, a leech simply disengages from his hostess and swims away to some secluded place, there to enjoy a postprandial doze that may last for days, weeks, or even months. On the other hand, if his thoughts turn instead to love, he seeks out a partner and does the business. A partner? Didn’t I just say that leeches were hermaphrodites? I did. But they still aren’t do-it-yourself fans, preferring to engage in what biology wonks term “reciprocal fertilization.” Among leeches, as among us, it takes two to tango. And who brings up the kids? Well, with only one exception that I know of, nobody. The fertilized eggs are deposited on “stones, plants, or trash, or buried in damp earth,” protected by a sort of cocoon. (Once again, the quoted words are Professor Morgan’s.) When the young hatch out, they’re on their own. The sole exception? Members of the Glossiphonidæ, who carry their fertilized eggs about with them, and whose offspring remain with their parents till they’re full-grown, clinging to the adults like tiny remoras—though, unlike remoras, the young leeches hold on with their tails.
Of course, Kathy wasn’t much interested in the life history of the leeches who were dining at her expense. She would have preferred to know in advance…
Where to Find ’Em
And then she’d have made sure she stayed away. But that’s easier said than done, I’m afraid. Leeches can be found throughout Canoe Country—and far beyond, in bodies of water ranging from streams and rivers to swamps to ponds and lakes, not forgetting irrigation ditches and rice paddies. Leeches also prefer shallow water to deep, and they don’t stray far from cover. Unfortunately, this describes the very places where paddlers are most likely to get their feet wet. So you don’t have to go looking for leeches. If you spend much time wading in weedy shallows, they’ll come looking for you. In other words, you can run but you can’t hide. Like blackflies and ticks, leeches are an integral (and inescapable) part of the paddler’s world.
So, what can you do about them? Perhaps the only answer is a rather unsympathetic one:
Deal With It!
It’s really not that hard. To be sure, none of us likes to find himself figuring prominently on some other creature’s menu, but at least leeches are content with our blood, and with pretty small quantities, at that. They’re not grizzlies. And while an oozing wound on a foot or ankle isn’t the most attractive souvenir of a trip, it’s not the end of the world. Fortunately, leech bites seldom pose a danger to otherwise healthy paddlers, though some individuals may experience an allergic reaction, and in rare instances these reactions can be severe. For the most part, however, good wound care—thorough cleaning, followed by the application of a protective dressing—should be enough. Direct pressure will help to stanch any bleeding.
First, though, you’ll have to remove the leech, and if you’ve ever seen The African Queen, you’ll probably reach for your salt shaker. Bad idea! The same goes for applying alcohol, insect repellent, or the end of a smoldering cigarette. A leech whose meal is interrupted in so inconsiderate a manner will express his displeasure by vomiting, thus increasing the likelihood of a subsequent wound infection. The upshot? Leave your salt in the shaker. Instead, just slide a fingernail gently under the uninvited guest’s oral sucker (it’s at the narrow end), breaking the seal. Easy does it. You don’t want to pull the leech off. You just want to dislodge him. Then, before he can resume feeding, do the same thing at the holdfast on the other end. A flick of your finger will finish the job. Remember, though, that if you turn your guest away early in his meal, you can expect some fairly intense itching at the site of the bite. Don’t scratch!
That was simple, wasn’t it? And if you want more detailed instructions, you’ll find them at WildMadgascar.org. But what if it’s not? Not simple, that is. Occasionally a leech will get up someone’s nose (or another convenient bodily orifice—convenient for the leech, at any rate). What then? It’s best to get the victim to a doc, if you can. Since the leech’s body will expand as he feeds, dislodging him from his hidey-hole may require surgical intervention. Don’t worry, though. Such situations are rare indeed, even if you’re hauling a steamer through the trackless channels of the Bora delta. They’re certainly nothing to lose sleep over.
Leeches don’t get much respect. You won’t find them on the posters that adorn office workers’ cubicles, and few environmental advocacy groups print up color calendars that include swimming leeches among the glossy images of bears and wolves and whales. Still, leeches are winning new friends among the medical community, and at least a few oddball naturalists admire their undulating elegance. Anglers also like them, though their appreciation is probably more practical than aesthetic. Is it too much to hope that a few paddlers will join the fan club? Probably. But who knows? A little knowledge isn’t always a dangerous thing. Leeches have their place. At their worst they’re a minor nuisance. And at their best? Well, the skillful leech deserves our admiration, even if he does occasionally put the bite on us. I think so, anyway. What about you?
Copyright © 2008 by Verloren Hoop Productions. All rights reserved.