Could the Cordyceps Fungus Really Take Over?

in tropical rainforests a war has been raging for millions of years a war between ant colonies and the different types of fungi that infect them it's a battle that has led to an arms race of evolution creating one of the most sinister methods of survival ever discovered parasites in general need a host animal to reproduce and survive and ants are a tempting host animal for parasites indeed up to 70 percent of the individual insects in a rainforest are ants in theory this should provide a large pool of potential victims for infectious and parasitic types of fungus thus just like our megacities ants face a huge risk of disease outbreaks that can potentially wipe out an entire colony therefore ants put up formidable defenses against such invasions they work together to groom each other clean of pathogens and if one of their comrades does get infected it is exiled from the colony and if a dead ant is discovered by its peers it is quickly removed then dumped far away from the colony before the disease can spread this is all a sometimes ruthless but effective way to keep diseases at bay but in the spinning wheel of evolution defenses like this can be outmaneuvered and overcome and one type of fungus has done this in an almost unimaginable way to see evidence of this strategy you'd need to venture deep into the rainforest in a place like thailand then you'd need to lean down and look for leaves that sit just above the forest floor and here on the underside of a leaf you just might find an example of a real life zombie an ant with its mandibles grasped tightly on the leaf's central vein devoid of its own life and instead hosting the life of a strange protruding fungus that is reproducing and spreading its spores days or even weeks of mind control have led to this moment the fungus working as the puppeteer the ant the unfortunate victim this type of mind control is very precise and very insidious and while we might hope it's isolated to ant on the forest floor parasites of all kinds are exceptional at altering the behavior of their hosts to increase the chances of transmission zombies in a sense are all around us how is such parasitic mind control possible and how scared do we need to be that parasites might take over our own minds [Music] the ant species camponotus leonardi a type of carpenter ant lives in the high canopy of the rainforest and builds an extensive network of aerial trails they would happily stay up in the treetops relative safety but sometimes their aerial network is imperfect if gaps between the leaves are too large to cross the ants are forced to descend to the forest floor and here is where the zombie fungus strikes the fungus ophiocordyceps unilateralis is a highly specialized infectious fungus when an ant stumbles across one of its spores the spore attaches to its exoskeleton and eventually breaks through using mechanical pressure and enzymes and at this point the fungus starts to take over over the course of the next week infected ants appear perfectly normal and go about their business undetected by the rest of the colony then once the fungus has developed enough inside the ant it compels the ant to leave the safety of its nest travel down to the forest floor and climb a small plant stem a few centimeters off the ground here the ant permanently clamps its jaws around a leaf and is completely overtaken by the fungus where the ant carries out its death grip is remarkably precise in one study every infected ant chomped down on the underside of a leaf and 98 bit down on the leaf's vein almost all of them did this on the north side of the plant on a leaf exactly 25 centimeters above the ground the chosen leaves were in an environment with 94 to 95 humidity and all ended up in a location with temperatures between 20 and 30 degrees celsius it is no coincidence that every one of these factors is the optimal condition for the cordyceps fungus to grow the zombie ant has transported it to its exact preferred location meaning the control the fungus exerts over the ant is astoundingly precise and at this precise location a long fungus stalk eventually bursts through the ant's head with a bulbous capsule full of spores on the end and the ant is killed and because the ant typically clamps down on a leaf in its own colony's territory the fungal spores rain down onto other ants below zombifying any it touches the first zombie ant was documented over a hundred years ago but until recently scientists had no idea how the cordyceps fungus could control the ant so precisely and while there are still many questions recent research using machine learning is getting us closer to an answer to get to the bottom of the mind control mystery scientists wanted to know what part of the ants body the fungus infects surely they thought the fungus mind control ability would be focused inside the ant's head so they worked to identify any parts of the ant where the fungus was present and to their surprise they found fungal cells not just in the ant's head but also in the thorax and gaster and intriguingly they also found fungal cells in abundance inside the legs next they wanted to see how much of the fungus infects the brain of the ant using a laser scanning microscope they examined the nervous tissue in the head of infected ants and found something profoundly unexpected the fungus doesn't touch the ant's brain at all fungal cells were concentrated directly outside the brain but none were observed inside the brain how can the fungus control the ants mind if its actual mind is untouched next they looked closer at the fungus growing in the rest of the ants body here they found fungal cells present between the muscle fibers in both the head and leg regions to quantify the amount of fungus in each sequential image scan they used a deep learning algorithm that could quickly identify fungal cells from ant tissue that could then build a 3d model doing this by hand would have taken months but instead they got the result in days scientists could then start to see that the hyphal bodies the yeast-like circular fungal cells were connected to other hyphal bodies by short tubes and that some of these hyphae invade the ants muscles penetrating the cell membranes and growing inside elsewhere in the fungal world fungal tubes like this are known to allow for the transfer of chemicals nutrients and information so these connections the tubes the penetrating fibers point to an intricate network inside the ant's body connecting the fungal cells to each other and to the ants muscles all of this suggests that the fungus isn't using mind control to transport itself where it needs to go but rather muscle control in a full body takeover the ant's mind may in fact be completely unaffected meaning it's trapped as a prisoner in its own body with the fungus in control exactly what chemical signals the fungus sends to the ant muscles to cause it to do its bidding is still unknown however scientists are working hard to uncover this last mystery of the ant zombie phenomenon but how common is this type of situation is it only ants that get zombified how worried do we need to be that the last of us may not be just science fiction but a premonition ants may be the most common host for the cordyceps fungus but they are by no means the only ones it infects plenty of other insects and spiders like tarantulas or beetles leading to a similar spectacular death however the cordyceps fungus does not have the zombifying ability in these other organisms only the ants and while this might make you want to breathe a sigh of relief the cordyceps fungus is far from the only parasite capable of controlling the behavior of its host in fact there are dozens of examples of parasitic mind control in the animal kingdom the leukocloridium is a parasitic worm that invades a snail's eyestocks where it pulsates in a mesmerizing way to imitate a caterpillar the worm then mind controls the snail out into the open to tempt hungry birds to eat its eyestalks once inside the bird the worm is able to reproduce and then release its eggs in the bird's droppings which then get eaten up by more snails and the parasite's life cycle is complete then there's the emerald cockroach wasp that attacks cockroaches with venom that blocks a neurotransmitter that allows the cockroach to control its own movements the wasp can then lead the walking zombie roach into the wasp's nest where it will act as a host and a food source for the wasps larvae all of these zombie instances seem to happen on a tiny scale on the forest floor with snails insects or spiders is it possible for more complex animals to fall victim to such an insidious killer for mammals it's certainly not as common but not unheard of in perhaps the most disturbing example of zombie infection in mammals mice become mind controlled by a parasite called toxoplasma gondii which compels them to walk straight to their own deaths toxoplasma gondii is a parasitic protozoan that can infect any warm-blooded animal but mice have particularly bad luck because there is just one animal that the parasite can reproduce in cats studies have shown that toxoplasma infection in rodents is able to change their instinctual fear of the odor of cats into an attraction to this odor the infected mice and rats visit more often and stay longer in places containing the odor of cat urine this naturally makes them more likely to get eaten by a cat where the toxoplasma parasite can complete its life cycle and unfortunately for us we too can get infected with this parasite in fact one third of the entire population already is infection usually occurs by eating undercooked contaminated meat or exposure from infected cat feces the parasite then hangs out in various tissues including the brain pretty much dormant for long periods of time sometimes for the rest of your life for decades scientists thought that the infection in humans was relatively harmless besides the risk it poses to unborn babies in pregnant women but recent studies show that that might not be the case at all and it might mess with us in very weird ways a study in 2002 showed that individuals involved in car accidents were more likely to have such infections hiding in their bodies it's thought that the toxoplasma parasite slows down reaction times in rodents this slow reaction time would help them get eaten by cats in us is it just an unfortunate evolutionary carryover or something more a few years later a small study found something even more strange participants with a toxoplasmosis infection rated the odor of diluted cat urine as more pleasant than non-infected participants did however weirdly this was only true for the men in the study and perhaps even more scary is that the toxoplasma parasite also seems to be a risk factor in developing schizophrenia researchers in copenhagen found that individuals with the infection were almost 50 percent more likely to be diagnosed with schizophrenia disorders compared to those without an infection scientists are still debating about the mechanism here and about the causation correlation conundrum but as the years go on the evidence only gets stronger for the idea that toxoplasma is absolutely messing with human psychology and behavior but is there a bigger reason that this happens the toxoplasma parasite mind controls the mouse to be able to reproduce and spread to other mice is toxoplasma gondii doing the same with us but humans are certainly not the prey of house cats the parasites current primary host as much as the cats may wish that were true but current is the key word here domesticated house cats have only been around for around 9 000 years it's likely that in the past a different bigger cat was the parasite's primary host and our ancestors may have been a primary snack leopards in particular are extremely good at hunting and eating primates and they always have been they are stealthy fast can leap into trees where primates sleep to snatch them and can carry heavy loads leopard ancestors have been going after human ancestors for millions of years even today leopards are the cause of 70 of baboon deaths and half of a leopard's diet consists of monkeys or chimpanzees to see if primates may be affected by the toxoplasma parasite the same way mice are researchers tested the reactions of chimps to the smell of leopard urine and they found that the chimpanzees not infected with toxoplasma investigated the smell of leopard urine less often avoiding the smell to the best of their ability the chimps infected with the toxoplasma parasite on the other hand investigated the leopard urine far more often their fear of it seemed to be diminished causing them to act more recklessly just like rodents infected with the parasite so somewhere in our evolutionary past it's possible that the parasite evolved to alter our decision-making skills as well or even attract us to our own feline deaths many of these studies were small and much more research needs to be done to fully understand the impact of toxoplasma gondii on our brains but these results so far have scientists reconsidering everything they thought they knew about the parasite while the cordyceps fungus may never bring about the zombie apocalypse in humans our actions and behaviors may still be influenced by a parasitic force that definitely does not have our best interest at heart to me fungi are one of the most fascinating mysterious sometimes scary and sometimes charming organisms in our world they help break down wood decompose leaf litter and create soil they create things essential to us like penicillin and aid in the production of cheese bread and beer they can give us sources of tons of vitamins or minerals and decorate our forest floors with whimsy or they can be so poisonous that they kill you almost instantly or take over brains and create leagues of zombie insects fungi in a sense control our world and life as we know 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Channel: Real Science

Views: 3,595,774

Keywords:

Id: jM5jf-8ekVA

Length: 18min 41sec (1121 seconds)

Published: Sat Oct 30 2021

Reddit Comments

[u/Volkera]

Every day I realize there's no gods

[u/randomguy1972]

"The last of us" video games are based on this.

[u/Rich_Alone]

The narration sounds like someone trying to be interested and bored at same time