I suspected he was outside his malarial zone of expertise, but he assured me that a scientist in Israel studied the wasps and was figuring out how they turn cockroaches into hosts for their offspring. So I contacted the scientist, one Frederic Libersat at Ben Gurion University. It turned out that the wasps were real. And they were stranger than I could imagine.
The wasps are beautifully named in both Latin and English: Ampulex compressa, aka the jewel wasp. When a female Ampulex is ready to lay her eggs, she seeks out a cockroach. Landing on the prospective host, she delivers two precise stings. The first she delivers to the roach’s midsection, causing its front legs to buckle. The brief paralysis caused by the first sting gives the wasp the luxury of time to deliver a more precise sting to the head.
The wasp slips her stinger through the roach’s exoskeleton and directly into its brain. She continues to snake her stinger—a bit like a surgeon snaking his way to an appendix with a laparoscope—until she reaches the particular knot of neurons that produces the signals that prepare a cockroach to start walking. The wasp injects a second venom that quiets those neurons down so that the cockroach cannot make itself move.
From the outside, the effect is surreal. The wasp does not paralyze the cockroach. If the cockroach is spooked, it will jump, but it will not run away. The wasp then takes hold of one of the roach’s antennae and leads it, like a dog on a leash, to its doom: the wasp’s burrow. The roach creeps obediently inside and sits there quietly as the wasp lays her egg on its underside. The wasp then leaves, sealing the burrow and entombing the still-living cockroach.
The egg hatches, and the larva chews a hole in the side of the roach. In it goes. The larva grows inside the roach, devouring the organs of its host, for about eight days. It is then ready to weave itself a cocoon, which it makes within the roach as well. After four more weeks, the wasp grows to an adult. It breaks out of its cocoon, and then out of the roach.
The sting is what fascinates scientists like Libersat most. Ampulex does not want to kill cockroaches. It doesn’t even want to paralyze them the way spiders and snakes do, since it is too small to drag a big paralyzed roach into its burrow. Instead, it just delicately retools the roach’s neural network to take away its motivation. Its venom does more than make roaches zombies. It also alters their metabolism so that their intake of oxygen drops by a third. The Israeli researchers found that they could also drop oxygen consumption in cockroaches by injecting paralyzing drugs or by removing the neurons that the wasps disable with their sting. But they can manage only a crude imitation of the wasp’s venom; the manipulated cockroaches quickly dehydrated and were dead within six days.
The wasp venom somehow puts the roaches into suspended animation while keeping them in good health, even as a wasp larva is devouring it from the inside. Scientists don’t yet understand how Ampulex manages either of these feats. Part of the reason for their ignorance is the fact that scientists still have much to learn about nervous systems and metabolisms. But millions of years of natural selection has allowed Ampulex to reverse engineer its host. We would do well to follow its lead and gain the wisdom of parasites.
I could not believe at first that I could have written an entire book on parasites and miss a marvel like the jewel wasp. But as the years pass, I continue to learn of more parasites, each of which that brings back that old familiar feeling of spooky respect. There are simply too many parasites for anyone to appreciate them in full. And the catalog of parasites grows each year, as scientists discover new ones. In 2009, I discovered that one of those parasites had been named after me.
The news came from a young parasitologist named Carrie Fyler. In college, Fyler was not sure what to do with her life. She was captivated by parasites but couldn’t believe that a life could be made out of that passion. Then she read Parasite Rex and changed her mind. She went to graduate school at the University of Connecticut to study with the parasitologist Janine Caira. Caira’s specialty is the study of tapeworms that live in sharks and their relatives. Fyler has traveled with Caira to places like Senegal and Chile in order to dissect fish and pluck out their tapeworms. Fyler wrote her dissertation about a genus of tapeworms called Acanthrobothrium, which includes 165 known species. As part of her research, she examined some mysterious Acanthrobothrium tapeworms that Caira and her colleagues had discovered on a 1999 voyage aboard the Ocean Harvest, a commercial trawling ship sailing the Arafura Sea off the north coast of Australia. The fisherman pulled up a massive whip ray belonging to a species never seen before. Caira was more interested in its tapeworms, which were equally new to science.
There are about 1.8 million species of animals, plants, fungi, and microbes that have names. There are many millions more still to be named. Each year, scientists name tens of thousands of new species, which means that they have centuries to go before they finish the job. We name our children as soon as they’re born, but naming a new species comes long after its discovery. Once scientists find an organism that looks like it just might not belong to any known species, they search the scientific literature to see if it is indeed new to science. If it is, they inspect it in painstaking detail, observing all the information one might be able to use to identify another organism as belonging to the same species. This is not the sort of work a genesequencing robot can do for you on your lunch break. This is natural history, old school.
There are some 6,000 species of tapeworms named so far, but scientists regularly discover new ones. When Fyler examined the whip ray tapeworms Caira gave her, she discovered that they were five new species. As she began to describe them, she decided to name one of them Acanthobothrium zimmeri.
I’m happy to report that A. zimmeri is a fine parasite. It has the bizarre anatomy that you’d expect from a tapeworm—an animal that has abandoned brains, eyes, and mouth and has turned its skin into inside-out intestines. Its head is festooned with a distinctive set of suckers, hooks, and muscular pads, which presumably it uses to clamp onto the gut of its host. Like other tapeworms, the rest of its tiny body is made up mostly of segments, each of which carries both testes and ovaries. (I note, without comment, that in her Folia Parasitologica paper, Fyler describes the vagina on each segment of A. zimmeri’s body as “thick-walled, sinuous.”)
When I first discovered I was going to have a species named for me, I was overwhelmed by delusions of grandeur. But eventually I came back down to earth. My fall came in Arlington, Texas, where I had traveled to attend a meeting of the American Society of Parasitology. I got into a hallway conversation with Fyler and another cestodologist about the newly named A. zimmeri.
“Yeah, I guess that makes sense,” he said, sizing me up. “Acanthrobothrium is kind of tall and thin like you.”
Naming species was not in fact the hallowed ritual I had imagined. With so many species to name, it is actually rather routine. Fyler named the other four tapeworms Caira found in the whip ray for:
1. the ship that Caira and Jensen were on (A. oceanharvestae)