I found an article on Digg this morning about this parasitoid wasp. This subject fascinates me. The page they linked was inaccessible, but Wikipedia has a great article about it.
Ampulex compressa (Emerald Cockroach Wasp) delivers an initial sting to a thoracic ganglion of a cockroach to mildly paralyze the front legs of the insect. This facilitates the second sting at a carefully chosen spot in the cockroach’s head ganglia (brain), in the section that controls the escape reflex. As a result of this sting, the cockroach will now fail to produce normal escape responses.
The wasp, which is too small to carry the cockroach, then drives the victim to the wasp’s den, by pulling one of the cockroach’s antennae in a manner similar to a leash. Once they reach the den, the wasp lays an egg on the cockroach’s abdomen and proceeds to fill in the den’s entrance with pebbles, more to keep other predators out than to keep the cockroach in.
A fascinating parasitic fungus which also alters the behavior of its host is Cordyceps Lloydii. I couldn’t find a Wikipedia article about it, but there’s an amusing web page the purpose of which I can’t reckon.
This fungus has evolved the ability to control the minds of the ants it infects. The process begins when the ant unwittingly ingests a spore of Cordyceps Lloydii as its walking along the forest floor. The spore makes its way through the ants body, eventually reaching the brain. Once in the brain, the spore begins to control the behavior of the ant who suddenly finds himself searching for the stalk of tall plant and climbing skyward. Fully under the control of the fungus in his brain, the ant impulsively climbs to the highest leaf where he grasps the leaf with all of his strength, his claws hardening with an uncontrollable expenditure of energy. At this moment, Cordyceps Lloydii enjoys the fruits of its labor.
A grotesque mushroom sprouts from the fungal mush that was once the ant’s brain. Bursting from underneath the smooth surface of the ant’s head, the long stalk extends skyward. Now, taking advantage of the healthy breeze available at such high altitudes, the stalk releases its fresh spores into the wind. Having served its purpose by helping the spore to this favorable altitude, the ant dies, adorned with the freakish funerary ornaments of its murderer. Carried by the wind, the spores drift to the forest floor where they will infect more ants.
And in another case of a parasite taking control of an ant’s arm control nerve, Dicrocelium dendriticum starts life as an egg in the intestines of cows. Cow dung is fed upon by snails who become infected and serve as a breeding ground for the fluke, who then uses the snail’s slime as a handy slip and slide escape route. Then…
Ants happen upon the slime and consume it as a source of moisture thus taking the new flukes into their system. Once inside, the parasite shows an interesting tactic. By controlling nerve centers of the ant they are able to control its behaviour. When the sun sets and temperatures drop the ant is compelled to attach itself to a tall blade of grass by its mandibles. Here it waits to be ingested by some grazing animal. If the ant survives the night the sun prompts it to return to the colony and live its life normally, until the next night. Eventually the ant is eaten by some grazing animal.
And then there’s my current nemesis, Toxoplasmosa gondii.
In a series of experiments, [scientists] demonstrated that healthy rats will prudently avoid areas that have been doused with cat urine. In fact, when scientists test anti-anxiety drugs on rats, they use a whiff of cat urine to induce neurochemical panic. However, it turns out that Toxoplasma-ridden rats show no such reaction. In fact, some of the infected rats actually seek out the cat urine-marked areas again and again. The parasite alters the mind (and thus the behavior) of the rat for its own benefit.
By some estimates, almost half the human population of earth is infected with this parasite. Recent research shows that it also has an effect on human minds, making us stupid and slutty! So if you’re feeling 10 to 15 IQ points below your norm or find yourself sleeping with someone simply because they seem to enjoy your uninhibited manner, check to see if it’s not just the booze, then seek treatment. Medications to treat the infection include those used with most other protozoal infections, like pyrimethamine, sulfonamide drugs, folinic acid, clindamycin, and trimethoprim-sulfamethoxazole.
Yes, Wikipedia sort of sucked me in for a few minutes this morning.