Natural History: Private choices - Endpaper - tenacity of a freshwater leech

The kick screen was weighed down with a slime of wet, fallen leaves and hairy algae. The children hauled it from the creek bed onto a level place along the bank. There they eagerly knelt beside it and, with forceps, began to grasp anything that moved, transferring their finds to white plastic ice-cube trays filled with creek water. The fourth-graders, from the town of Saint George in northeastern Kansas, were taking part in a project called Streamshot, and our purpose was to measure the environmental health of Blackjack Creek. Our assessment would be simply an index of its macroinvertebrates, a sampling of small but not microscopic animals widely used as indicators of freshwater quality.

The children's trays began to fill with mayfly nymphs, aquatic sow bugs, and the larvae of blackflies, caddis flies, and bloodred midges. And clinging to the slippery underside of the very last leaf was a leech. Teased from its tenuous hold, the leech slid into one of the tray's compartments and immediately sensed a change in its surroundings. Suctioning itself to the bottom of the tray, it accordioned its way around the confines of the strange white room, then reared up like a rising periscope to take a look around.

The kids shrieked with joy, awe, and horror. "Watch out! It'll suck your blood!"

I assured them that this was a vegetarian leech.

"How do you know?"

"Well, it was on a leaf, wasn't it?"

Finally they calmed down to watch its sinuous movements with fascination.

I usually released our captured "macros" at the end of our surveys, but on that day I had agreed to preserve them as specimens for the school's reference collection. Sometimes we have to make tough choices. I dumped the contents of the ice-cube trays into a jar and screwed on the lid.

Later that afternoon I deposited the jar in the refrigerator of the education department office. But the fridge wasn't working properly, and when I returned to retrieve the jar several days later, the water--and everything in it--was frozen solid. I thrust it quickly into a nearby microwave oven, then began delicately separating the lifeless invertebrates and tweezing them into individual specimen jars filled with alcohol and water.

Suddenly a gliding movement in the bottom of the collection jar caught my eye. The leech was alive! Somehow the creature had survived the freezing and thawing unscathed. I dumped the contents of the jar into a pie pan, and there the leech continued its exploratory behavior, alternately squeeze-boxing its finely segmented body into a tight ball and expanding to a full inch and a half.

I was amazed and humbled by its grit. I put the animal in my palm and felt a slightly pleasant sensation as it crept along my "life line." Its personal specimen jar was labeled and waiting. I hesitated, then dumped the alcohol mixture from the specimen jar, rinsed it, and filled it with the thawed creek water. I tweezed the now frantically squirming leech into the container, put it into a shoebox with the rest of the collection, and headed for home.

After dinner I peeked into the shoebox: the leech had climbed to the top of its jar and was huddled inside the lid. "Enough of this" I thought. Shoving the jar into my coat pocket, I rummaged for my car keys and drove to the banks of Blackjack Creek, parking at the spot where we had collected our samples. After tossing the jar's contents into the dark water, I watched the flowing creek in the beams of my headlights for a few more minutes. Nothing stirred on the surface. The leech was home free. Sometimes our choices become epiphanies.

Dru Clarke taught marine science and ecology in secondary school for thirty-one years. She lives in the Flint Hills of northeastern Kansas.