Essays

Wild On The Prairie: Invertebrates

Leeches in the Pond
December 9, 2001

Several boys, ages 7 to 12, drop by the Sibley Nature Center at least once a week. Sometimes they help do a housekeeping chore, other times they help him do a project out on the trail. It is a "club," without the formal structures of adult organization. The boys proudly say that they "work" for Sibley. The other day their "job" entailed going to the pond and attempting to catch leopard frogs for Lee Ellis, one of the Museum of the Southwest's Children Museum staff members. She needed five for a presentation at the Washington Elementary Magnet School Friday after-school program.

Dylan, Michael, Chris, and Drake ran into the building, screaming in a painful volume --" We caught a leech, we caught a leech, we caught a leech," and danced around him as he held the bottle and peered at the leech. Brandon Young, who worked for Sibley at the time, complimented them on their observational skills -- for the leech was smaller than a person's littlest fingernail, and the color of the soupy mud in which it squiggled.

Brandon and the boys moved on to other projects and other subjects of conversation. Dauna, another Sibley volunteer and a student at Midland College, picked up the bottle to examine the leech, and having an artist's sense of detail noticed the dozen tiny babies attached to the ventral side. She called the boys to come back and take a look and commented that a leech had attached itself to her once. "OOOh gross!" Until then none of the boys had reacted with that most common response to the Hirudinea.

44 freshwater species of leech inhabit the United States. Most are predators or scavengers, with only a few species taking blood from warm-blooded animals. The species common to West Texas shaped like an oval with one end much bigger than the other. At one end is the mouth, and at the anal end is a sucker that holds on tight to its favored substrate. Other species of American leeches can be brightly colored, and have the ability to change color by enlarging or shrinking chromatophores containing different colored pigments.

Brandon and I studied Pennak's "Freshwater Invertebrates" and to the best of our ability believe our species is Glossiphonia complanata, a specialist that only feeds on snails. I took the specimen to Andrew Franks, a physics teacher at Lee High School, who photographed it. His 6th grade daughter Erin kept asking what I planned to do with the creature.

"Make a pet of it -- keep it in the jar and feed it."

"How gross -- it is nasty and ugly --"

"You "speciesist", you are condemning the critter, calling it evil and horrible just because it is a leech. You are expressing such a virulent hatred of this tiny little animal. It is such an innocuous thing. Why--"

"Because it is slimy, and leeches suck blood, they are gross and --"

"It is wonderfully bizarre -- look at it -- it is a shapeshifter, one second it is a ball, then it stretches over an inch long, and it flips upright if you roll it over, and it has maternal instincts -- see, she is reaching over for the baby that we knocked off getting it into the petri dish."

"Take that nasty thing and get it out of the house --" Erin was laughing as she pointed at the door.

In warm shallow water with plants and debris unbothered by wave action, population densities of 700 leeches per square meter have been reported. Frank Collinson, an early day buffalo hunter here on the Llano Estacado reported such a population density of what had to be the horse leech Haemopis marmorata. Leeches are chiefly nocturnal, and prefer to remain hidden. Some species can survive in intermittent ponds by burrowing into the mud and constructing a mucus-lined cell, aestivating for as long as a month. Winters are spent in the same manner. The horse leech crawls about on the ground after a rain, sometimes going as far as 400 yards from the water. On such forays they eat earthworms that emerge after the rain.

Duck leeches are likely to be present also, in playa and stocktank waters on the Llano Estacado. Brandon remembered a professor saying in a lecture that they attach themselves to a duck's cloaca. I did not find verification of that, but I found a reference that mentioned duck leeches fill the nasal chambers of ducks, so many that clumps of writhing leeches protrude from the nostrils. If you see a redhead sneezing, they are expelling the leeches, and green-winged teal scratch their bills in flight for the same reason.

Many species of leeches are hermaphroditic, possessing a pair of ovaries and several pairs of testes. They avoid inbreeding by finding partners. Fertilization can be a pain -- sperm-containing spermatophores are attached to the partner's skin. These spermatophores produce destructive enzymes that eat away the other leech's flesh, enabling the sperm to enter its body, where they become suspended in the blood and are carried to the ovaries. Three days later, the holes bored by the spermatophores heal.

Observing, photographing and researching the leeches turned out to be so much fun we forgot to try to catch those frogs. Sorry, Ms. Ellis -- I hope the one frog we had on hand performed the experiment adequately!