Though merely a cousin of the lowly toadstool, the Cordyceps fungus lives a life that could hardly be imagined by even the most creative science-fiction writer. Cordyceps lies quiescent on the forest floor, waiting for its unsuspecting insect prey to pass. When a bug wanders by, the fungus attaches itself to the insect exoskeleton. It then secretes a chemical that burns a hole in the insect's body armor. Next, Cordyceps inserts itself into the insect body and proceeds to devour all of the host's nonvital organs, all the while preventing the insect from dying of infection by secreting an antibiotic and a fungicide (as well as an insecticide to deter other insect predators). Once the nonvital organs are consumed, the fungus eats part of the insect brain, causing the insect to ascend to the top of a tall tree in the forest. At this point, Cordyceps devours the rest of the bug's brain, thereby killing the insect and causing the body to split open. At that point, the fungus can release its spores a hundred feet above the forest floor." !!!
http://bugguide.net/node/view/7300/bgimage
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Sometimes they achieve this change indirectly, by manipulating hormones that affect the nervous system. There are barnacles (Sacculina granifera), a form of crustacean, found in Australia that attach to male sand crabs and secrete a feminizing hormone that induces maternal behavior. The zombified crabs then migrate out to sea with brooding females and make depressions in the sand ideal for dispersing larvae. The males, naturally, won't be releasing any. But the barnacles will. And if a barnacle infects a female crab, it induces the same behavior -- after atrophying the female's ovaries, a practice called parasitic castration.
http://en.wikipedia.org/wiki/Sacculina
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Leucochloridium paradoxum(a flat worm) finds a snail and takes control. It forces the snail to climb up to the top of vegetation where it can be seen by birds. It then makes the snail's tentacles pulsate like a caterpillar so as to attract attention to itself. Bird notices & consumes snail. The flatworm then reproduces in the bird, lays eggs which the bird poops out.. snail eats poop, rinse & repeat:
http://people.smu.edu/eheise/Leucochlor ... adoxum.htm
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και το Τοξόπλασμα: (αυτό και το παραπάνω για τα καβούρια είναι από ένα άρθρο με τίτλο Bugs in brain)
a beautifully specific case of brain control, as described by Manuel Berdoy and colleagues at the University of Oxford as they studied a parasite called Toxoplasma gondii. In a toxoplasmic utopia, life consists of a two-host sequence involving rodents and cats. The protozoan gets ingested by a rodent, in which it forms cysts throughout the body, particularly in the brain. The rodent gets eaten by a cat, in which the toxoplasma organism reproduces. The cat sheds the parasite in its feces, which, in one of those circles of life, is nibbled by rodents.
The whole scenario hinges on specificity: Cats are the only species in which toxoplasma can sexually reproduce and be shed. Thus, toxoplasma wouldn't want its carrier rodent to get picked off by a hawk or its cat feces ingested by a dung beetle. Mind you, the parasite can infect all sorts of other species; it simply has to wind up in a cat if it wants to spread to a new host.
This potential to infect other species is the reason all of those 'what to do during pregnancy' books recommend banning the cat and its litter box from the house and warn pregnant women against gardening if there are cats wandering about. If toxoplasma from cat feces gets into a pregnant woman, it can get into the fetus, potentially causing neurological damage. Well-informed pregnant women get skittish around cats. Toxoplasma-infected rodents, however, have the opposite reaction. The parasite's extraordinary trick has been to make rodents lose their skittishness.
All good rodents avoid cats -- a behavior ethologists call a fixed-action pattern, in that the rodent doesn't develop the aversion because of trial and error (since there aren't likely to be many opportunities to learn from one's errors around cats). Instead, feline phobia is hard-wired. And it is accomplished through olfaction in the form of pheromones, the chemical odorant signals that animals release. Rodents instinctively shy away from the smell of a cat -- even rodents that have never seen a cat in their lives, rodents that are the descendants of hundreds of generations of lab animals. Except for those infected with toxoplasma. As Berdoy and his group have shown, those rodents selectively lose their aversion to, and fear of, cat pheromones.
Now, this is not some generic case of a parasite messing with the head of the intermediate host and making it scatterbrained and vulnerable. Everything else seems pretty intact in the rodents. The social status of the animal doesn't change in its dominance heirarchy. It is still interested in mating and thus, de facto, in the pheromones of the opposite sex. They simply don't recoil from cat pheromones. This is flabbergasting. This is akin to someone getting infected with a brain parasite that has no effect whatsoever on the person's thoughts, emotions, school test scores, or television preferences but, to complete its life cycle, generates an irresistible urge to go to the zoo, scale a fence, and try to French-kiss the pissiest-looking polar bear. A parasite-induced fatal attraction, as Berdoy's team noted in the title of its paper.
τα κουφά της εξέλιξης
), και το βάζω και εδώ με περισσότερα στοιχεία.
