I read Carl Zimmer’s Parasite Rex some time last year and grossed out not just a few of my friends when telling them what I had learned during polite dinner conversation: From parasites that alter the brain chemistry of cats (and possibly humans) so as to make them more sexually promiscuous to the protozoa that cause malaria and almost completely reengineer the red blood cells in which they live to wasps that lay their eggs into living caterpilars, which are then slowly eaten alive by the hatching wasp larvae.
On the one hand, I found it absolutely fascinating what clever strategies parasites have evolved to get from one host to another and to defeat a host’s defenses (an ability which we may soon be able to harness to cure bad cases of allergy). But on the other, there were times when even I got so grossed out that I just had to put the book down for fear of not being able to live a normal life ever again.
And so, in the spirit of sharing, I thought I’d give you, too, a glimpse into the world of parasitism. There is a short Carl Zimmer essay, which is taken from the book and gives you a pretty good idea of how imporant but still underestimated a phenomenon parasitism is. The essay is provocatively entitled “Do Parasites Rule the World?“:
“Every living thing has at least one parasite that lives inside or on it, and many, including humans, have far more. Leopard frogs may harbor a dozen species of parasites, including nematodes in their ears, filarial worms in their veins, and flukes in their kidneys, bladders, and intestines. One species of Mexican parrot carries 30 different species of mites on its feathers alone. Often the parasites themselves have parasites, and some of those parasites have parasites of their own. Scientists have no idea of the exact number of species of parasites, but they do know one fact: Parasites make up the majority of species on Earth. Parasites can take the form of animals, including insects, flatworms, and crustaceans, as well as protozoa, fungi, plants, and viruses and bacteria. By one estimate, parasites may outnumber free-living species four to one. Indeed, the study of life is, for the most part, parasitology.”
Carl Zimmer also writes the excellent blog The Loom, which has become my go-to-blog for anything related to biology and the theory of evolution.