It might sound like something out of sci-fi, but plenty of parasites can control the minds of caterpillars, roaches, crabs, and maybe even us. In many cases, scientists don't know exactly how these creatures achieve mind control.
This spider, Plesiometa argyra, is an expert builder of perfectly round webs. But with one sting, a parasitic wasp can take over its mind.
The wasp deposits its larvae inside the spider's body, along with a new blueprint--instead of building its web, the spider spends the last night of its life constructing a silk cocoon, which becomes a home for its killers.
When the silk sack is done, the larvae kill the spider. Then they take up residence in the cocoon, suspended safely above the predators of the rainforest floor.
Humans might not be exempt from the mind control of parasites, either. Half of us, scientists say, carry the parasitic protozoa Toxoplasma gondii. And once we have toxoplasma in our bodies, we carry it for life.
The rate of infection can vary wildly from country to country; only three percent of South Koreans have are infected by toxoplasma, while as many as 80 percent of French people are carriers. The Centers for Disease Control says that areas where people prefer undercooked meat, like France, or have stray cats running around, like Central America, are rife for infection.
Though the parasite's main host is the cat, it can live in thousands of warm-blooded species (and we're on the list). Toxoplasmosis, researchers have found, might make people more likely to be schizophrenic, and can change personality in subtle ways. One researcher found that infected men were more aggressive and jealous, women were more outgoing, and perhaps most seriously, both had slower reaction times and were in more traffic accidents.
Emotion researcher Jaak Panksepp
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