Parasite Rex: Inside the Bizarre World of Nature's Most Dangerous Creatures

In the beginning there were hydrothermal vents, and they said, "Let there be life." And life was formed and it was good. But life was lonely, so the vents said, "let there be parasites." But the parasites smote much of the other life akin to a great flood sweeping across the land. After 40 days and 40 nights, life and the new parasitic life form began to play the arms race game of the Red Queen and that was good. And other life begat more other life through cloning of their DNA's, but reproduction through cloning once again allowed parasites to gain dominion over the land and the seas, so other life invented immunology and other life invented sex, in self defense. And so it went. And it came to pass that there were many other life forms, but none existed without parasites, and no parasites existed without them, and the battle of the Red Queen escalated and flowed, lacking much ebb. As a parasite gained dominance over one species, other species proliferated, providing separation and new speciation. The peacock grew seemingly unnecessary featherages, the bower birds built elaborate seduction altars, and all the creatures created pecking orders and heirarchies. And so it went. And it came to pass the parasites evolved elaborate life cycles involving different life forms and serial hosts. In each host they cast spells which they called "better living through chemistry." Some intermediate hosts became mere parasite hotels, hypnotized into helping the parasite find its next host. The more vicious parasites, in error, killed their hosts, thereby they also died. The wiser ones preferred slavery i.e., how to get the most use and nutrition out of their host without killing it. Both the parasites and their more able hosts went to absurd extremes, each trying to outwit the other, in building Rube-Goldberg defense strategies. One minor two-legged (called "human") species went to such ridiculous extremes as to evolve elaborate cognition in order to best the parasites. They became so bright, they figured many things out about their world, yet these upright walkers were still not cognizant of the prominent role parasites had played in human evolution, and their dominance. Alas, for every member of their bigger group, mammals, there were thousand of groups of parasites. The parasites had come to make up the majority of the creatures on earth. And so it is. And the creatures that multiply across the face of the earth continue to thrive. And the hydrothermal vents who observe all of the Red Queen game say, "it is good," and they don't rest.

Once considered a "degenerate" form of life, parasites are being seen as important indicators of how evolution has progressed over 4 billion years. Zimmer credits them with being the driving force for biological diversity. He substantiates this claim with a sweeping, evocative survey of what is known today about parasites. That, he regretfully concedes, is little enough. What is known is that many early conceptions about parasites needed to be thrown aside as more information about this highly adaptable and widely variable range of organisms emerges. While we may recoil at the term "parasite", Zimmer identifies but one villain in this book. Ray Lankester, a devoted Edwardian-era evolutionist, postulated that parasites were a "regressive" form of organism. He thought they shed evolutionary advantages as they simplified their bodies through their life cycles. Lankester thus set the tone for generations - biologists avoided studying parasites as offering no additional information revealing evolution's processes. Zimmer explains that since parasites are predators, it was thought they ought to follow the patterns of other predators - stalking prey like lions, or following scent gradients like sharks. Instead, as more about them came to light, it was revealed how adaptive parasites are. Some, in fact, have developed the talent of making "prey" come to them. One fluke invades a snail early in its career. In an intermediate, but distinctive form, it then moves to an ant. Residing in the ant's brain, at some point it directs the ant to climb a grass stalk. There it waits for the grass, along with the ant and itself, to be eaten by a cow. The fluke cruises through the cow's stomach before taking up residence in the liver as adults, yet another body form. When the eggs are produced, they return to the intestinal tract to be later deposited on the ground, awaited by the snails. Looking at each phase, residing in a different host, you would be inclined to see it as a separate species. This note is but one of the endless chorus of parasite adaptations Zimmer relates in this excellent book. He joins the refrain of older scientists lamenting the lack of upcoming researchers needed in parasite studies. Unlike the animals we see around us, most parasites have astonishingly varied body forms as they go through the phases of their life cycles. For years, this catalog of body plans was thought to display different species. Only recently has it been demonstrated that these creatures changed shape and function dramatically as they changed living environments. Identifying each stage, the invader's function there, the impact on the host and other elements requires long, patient and dedicated work. Those of us in the urban world think we can keep parasites at a distance, flooding our farms and wetlands with chemicals to fend them off. This is false confidence, Zimmer reminds us. Parasites are the most adaptable forms of life on the planet.

I was drawn to this book orignially out of the idea that things so small can cause so much damage and or alter larger animals in ways some would find hard to believe. One of the previous reviewers mentioned something about sacculina (a parasitic barnicle that attacks crabs). Reading about how sacculina castrates its host and makes it care for its young was one of the things that got me interested in reading this fascinating book. Sacculina is only one of many fascinating parasites discussed however. Many are familiar with parasites such as cuckcoos, tape worms and trichinella but few have heard of parasites such as the lancet fluke and even fewer are familiar with its life cycle and what it does to its host. In terms of the spooky element, I think Dicrocoelium dendriticum (the lancet fluke) ranks as one of the top villains given in the book. The lancet fluke has three different hosts, namely the snail, the ant and cow or other grazers. As an adult, the lancet fluke spends its time in the gut of a cow where it lays its eggs. The eggs are then deposited on the ground with the cow's feces then snails eat the eggs which hatch in its intestines. The baby flukes bore through the snail's gut emerging from the snails slimy body and onto the ground where they attract the attention of ants. The ants eat these slime balls and become infected. The flukes then make the ants climb up the highest blade of grass they can find and lock their mandibles onto the top of the blade hanging until they are eaten by a grazer to continue its life cycle. There are a few interesting details which I intentionally left out.Only one parasite in the book made me cringe and that was with candiru. Candiru is a thin fish found in the rivers of Latin America. Woe to the unfortunate soul who happens to urinate in a river in the presence of candiru because it will detect the odor of urine and ram itself into the victim's urethra (male or female) and lodge itself there with its teeth. Candiru is virtually impossible to remove once inside the urethra. Humans are not candiru's natural hosts however, it attacks them as a mistake.The book also expounds on how and why parasites have a vital and critical role to play in ecology. Examples of bad things happening because certain parasites were eliminated is discussed.

I picked up "Parasite Rex" for the "yuck factor", the impulse that drives most of us to watch horror films, look at photos of car crash victims, etc. I came out of it educated, enlightened & impressed.Carl Zimmer acknowledges the "yuck factor" right away; his opening chapters discuss some of the more gruesome aspects of tapeworms, blood flukes, malaria & so on. But as the book progresses, the reader is drawn into a more objective view of the life cycles & natural history of the parasite; by the final third of "Parasite Rex", the reader discovers that without parasites planet Earth might never have evolved multi-celled creatures, sexual reproduction or immune systems! We learn from Zimmer that scientists are not only learning to use parasites to re-balance the ecological disasters mankind has wreaked, they are beginning to believe many modern maladies such as allergies & colitis are caused by the lack of parasites in urbanized humanity! "Parasite Rex" is clearly written for the layperson, with enough graphically gory details & photos to satisfy the most juvenile amongst us. It is in the way Zimmer turns the readers viewpoint around, from disgust to wonder, that is the real achievement of this book. Any person interested in the future of our planet should read it.

This is one of those rare books that can totally alter how you look at the world. Read it and you begin seeing parasites in every skin blemish you have. See a cat catch a mouse and all you can do is think about all the parasites its about the ingest. You find youself wanting to visit the parasite museum in Maryland to see all the horrible creatures you've been reading about. You begin thinking that Zimmer's right and that parasites have driven the evolution of the world. You begin wodering if Stephen King has read it and if so what novel he's writing. You begin wondering if there's thousands of little cysts in your brain and that your life goal of going on safari in Africa may need revaluated. You imagine what its like to extract a guinea worm from your leg. You question whether or not you will ever eat crab again. You wonder whether the reason you've been so hungry of late is because there's a sixty foot long tapeworm inside your intestines. It's a stunning book and an important one. Zimmer found something obvious that's been overlooked in biology and if he's right will change the way we view life. Survival of the individual will be changed to survival of the creature living inside the indiviual. For example, there is a parasite that gets inside a snail, takes it over, forces it climb a blade of grass and wait for a grazing cow to wander by and eat it. The cow is where the parasite wants to end up. The snail is just a vessel to reach the cow. The young of the parasite end up in cow pies which the snail eats and the cycle begins again. The complex world of flukes and tapeworms, of enslaved crabs and suicidal snails, of sleeping sickness and malaria, is like a car wreck: you want to turn away but you can't, you're compelled to look fearful of what you might see. As you explore the book you learn that these creatures are much more than revolting. I can't say you'll ever view them with sympathy, you can view them with respect -- and hopefully at a safe distance.