Parasites: Looking for a Free Lunch
Photographs by Darlyne A. Murawski
Text by Jennifer Ackerman
Leech, bloodsucker, cootie, vermin, flea. By popular reputation parasites are repugnant creatures, the ugly of the universe, the creepy, slimy, and weird. In ancient Greek the word parasitos means one who eats at the table of another. In nature these organisms seem to have lost their table manners. They invite themselves to lunch and then dine on their hosts, sucking blood, leaching nutrients, devouring whole organs. One fish parasite destroys the tongue of its victim, then settles itself in the tongue’s place.
For years parasites have been dismissed as odd sideshows in the natural world, grotesque in form and gruesome in act. But lately they are finding a new place in the biological spotlight. A growing cadre of scientists now see these organisms as subtle, complex creatures, admirable in their own way and much more powerful than anyone ever imagined. Parasites have profoundly shaped life for billions of years; many of the traits we see in plants and animals evolved in response to their presence. Parasites may have given the zebra its bold stripes, shaped the behavior of animals from crickets to horses, even changed human genes.
NGM 1997/10