Vermont. December 1, 2009

The canoe had been a gift so the color did not matter much to me but for the sake of this story it seems important to know that it was red. On this particular day the color of the canoe and one of the realities of the Connecticut River gave me a bit of a start.

The river reality is that the shores have been closely bordered by railroad tracks since the early 19th century. When the hydro dams went in beginning in the early 20th century the reservoirs expanded beyond the limits of the natural river creating “setbacks”, in essence lakes formed by certain dams that stored water between the railroad tracks and the newly expanded shoreline. There was little current in this particular setback, plenty of weeds and dead wood and a muck bottom; a perfect setting for the rest of this story.

I seldom look at the bottom of a canoe when getting it on the pickup after a trip on the river. Beach it, get your stuff out and then grab the gunwales close to the middle, lever the canoe up over your head and slip it up onto the canoe rack. Taking a step back to see that the canoe was properly centered I shuddered because the canoe bottom was covered with more than a dozen two inch long black and tan colored mucus covered tear drop shaped leeches. I may have been ambivalent about the color of the canoe but they sure weren’t.

Leeches are classified as annelids, segmented worms. Leeches evolved from the earthworm. A leech body is composed of 34 segments, the first 6 of which form their mouth. Leeches can be found nearly every place there is water including desert water holes and reportedly in the Antarctic. Due to their sensitive eye spots leeches are nocturnal, although leeches are active during daylight in the shadows under rocks, logs, and debris on the bottom. They are most active spring and summer. Leeches spend the winter buried in mud just below the frost line.

Science is undecided about the taxonomic status of the numerous species of leeches. In fact depending on the source there may be as many as1000 or as few as 500 species of leeches. Leeches are slippery to deal with in evolution too because they don’t leave fossils. Science attempts to establish their evolutionary history by genetically identifying the current leech populations in the world and then matching distinct populations to the separation of the continents. Leeches probably have been on earth for 230 million years.

When a leech sinks its teeth into a host it releases both an anesthetic insuring the bite does not alert the host and an anticoagulant that insures the puncture bleeds profusely. Leeches use their mucus and suction to draw blood, the suction is created by its mouth while its mucus contains an anti-clotting enzyme called hirudin. Leeches remain attached to their hosts until they become full at which point they fall off to digest. Leeches can survive for months on a single meal.

There are two ways to remove a leech. The first is to relax, watch the leech, and admire its color patterns and its biology while it finishes its meal. This could take half an hour OR you can firmly slide your fingernail towards the leech and push the head sideways to break its seal. The head is the smaller end; the large end is just holding the leech in place. After removal the wound should be cleaned and bandaged. You can apply ice or an antihistamine if it itches. Do not pull, burn, or salt a leech to remove it. These approaches allow time for the leech to regurgitate its meal into the wound increasing the risk of infection.

Leeches have both female and male reproductive organs and reproduce by reciprocal fertilization. Similarly to the earthworms, leeches use a cocoon formed around their body to hold their eggs and then slip the cocoon off their body.

The loathsome leech offers several goods to humans. Since the 1980s medicine has increased the use of leeches because its mucus contains a number of chemical compounds including the anti-coagulant hirudin that helps prevent heart attacks, strokes, opens veins and arteries and reduces swelling. Direct application of live leeches helps reestablish circulation during operations to reattach limbs.

Fishers should have some regard for the leech too. Leeches are important in the food chain of an aquatic ecosystem acting not only as parasites but prey so live and imitation leeches (wooly bugger flies) are a good all-round offering for freshwater game fish including trout.

So give those nasty looking, slippery, blood sucking worms some respect. They may someday save your life or limb or hook you that whopper of a fish. As I whisked the leeches onto a paddle in order to throw them back into the water I just had to wonder, did the leeches feel cheated by the lack of blood from this large red creature?

David Deen is River Steward for the Connecticut River Watershed Council. CRWC has been an articulate voice for the Connecticut River for more than half a century.