A herd of wildebeests, a shoal of fish, a flock of birds. Many animals gather in large groups that are among the most wonderful spectacles in the natural world. But why do these groups form? The common answers include things like seeking safety in numbers or hunting in packs or gathering to mate or breed, and all of these explanations, while often true, make a huge assumption about animal behavior, that the animals are in control of their own actions, that they are in charge of their bodies. And that is often not the case.
Krdo zveri, jato riba, jato ptica. Dosta životinja se skuplja u velike grupe koje su među najlepšim spektaklima u svetu prirode. Ali zašto se formiraju ove grupe? Česti odgovori su oni poput traženja bezbednosti u grupi ili lova u čoporima ili skupljanja radi razmnožavanja, i sva ova objašnjenja, iako su često tačna, prave puno pretpostavki o ponašanju životinja, da životinje kontrolišu svoje radnje, da kontrolišu svoje telo. To često nije istina.
This is Artemia, a brine shrimp. You probably know it better as a sea monkey. It's small, and it typically lives alone, but it can gather in these large red swarms that span for meters, and these form because of a parasite. These shrimp are infected with a tapeworm. A tapeworm is effectively a long, living gut with genitals at one end and a hooked mouth at the other. As a freelance journalist, I sympathize. (Laughter) The tapeworm drains nutrients from Artemia's body, but it also does other things. It castrates them, it changes their color from transparent to bright red, it makes them live longer, and as biologist Nicolas Rode has found, it makes them swim in groups. Why? Because the tapeworm, like many other parasites, has a complicated life cycle involving many different hosts. The shrimp are just one step on its journey. Its ultimate destination is this, the greater flamingo. Only in a flamingo can the tapeworm reproduce, so to get there, it manipulates its shrimp hosts into forming these conspicuous colored swarms that are easier for a flamingo to spot and to devour, and that is the secret of the Artemia swarm. They aren't sociable through their own volition, but because they are being controlled. It's not safety in numbers. It's actually the exact opposite. The tapeworm hijacks their brains and their bodies, turning them into vehicles for getting itself into a flamingo.
Ovo je artemija, vrsta škampi. Verovatno su vam poznatije kao morski majmuni. Male su i obično žive same, ali mogu da se skupljaju u velika crvena jata koja idu metrima u širinu, a stvaraju se zbog parazita. Ove škampe napada pantljičara. Pantljičara je dugo, živo crevo sa genitaljama na jednoj i kukastim ustima na drugoj strani. Kao honorarni novinar, imam saosećanja. (Smeh) Pantljičara izvlači hranljive sastojke iz tela artemije ali radi i druge stvari. Kastrira ih, menja njihovu boju iz providne u jarko crvenu, čini da žive duže, i kako je otkrio biolog Nikolas Roud, čini da plivaju u grupama. Zašto? Zato što pantljičara, poput mnogih drugih parazita, ima komplikovan životni ciklus gde postoji dosta različitih domaćina. Škampi su samo jedan deo puta. Krajnje odredište je ovo, ružičasti flamingo. Pantljičara može da se razmnožava samo u flamingu, tako da bi do njega došla, manipuliše domaćinima škampima da stvore ova upadljiva crvena jata koja će flamingo lakše primetiti i pojesti, i to je tajna jata artemija. Nisu društvene svojom voljom, već zato što ih neko kontroliše. Ne radi se o bezbednosti u grupi. Zapravo je sasvim suprotno. Pantljičara zaposeda njihove mozgove i tela, pretvarajući ih u sredstvo za dolazak do flaminga.
And here is another example of a parasitic manipulation. This is a suicidal cricket. This cricket swallowed the larvae of a Gordian worm, or horsehair worm. The worm grew to adult size within it, but it needs to get into water in order to mate, and it does that by releasing proteins that addle the cricket's brain, causing it to behave erratically. When the cricket nears a body of water, such as this swimming pool, it jumps in and drowns, and the worm wriggles out of its suicidal corpse. Crickets are really roomy. Who knew?
Evo još jednog primera manipulacije parazita. Ovo je cvrčak samoubica. Cvrčak je progutao larve gordijevog crva, ili crva konjske dlake. Crv unutar njega raste do odrasle veličine ali mora da dođe do vode kako bi se razmnožavao, i to radi tako što oslobađa proteine koji zbunjuju mozak cvrčka zbog čega se ponaša pomahnitalo. Kada se cvrčak približi vodi, poput bazena, uskače i davi se, a crv se izmigolji iz tela koje je izvršilo samoubistvo. Cvrčci su baš prostrani. Ko bi rekao?
The tapeworm and the Gordian worm are not alone. They are part of an entire cavalcade of mind-controlling parasites, of fungi, viruses, and worms and insects and more that all specialize in subverting and overriding the wills of their hosts. Now, I first learned about this way of life through David Attenborough's "Trials of Life" about 20 years ago, and then later through a wonderful book called "Parasite Rex" by my friend Carl Zimmer. And I've been writing about these creatures ever since. Few topics in biology enthrall me more. It's like the parasites have subverted my own brain. Because after all, they are always compelling and they are delightfully macabre. When you write about parasites, your lexicon swells with phrases like "devoured alive" and "bursts out of its body." (Laughter)
Pantljičara i gordijev crv nisu sami. Deo su čitave armije parazita koji kontrolišu um, gljiva, virusa, crva, insekata i ostalog koji se svi usavršavaju u podrivanju i zaobilaženju volje svojih domaćina. Prvi put sam saznao za ovaj način života kroz "Procese života" Dejvida Atenboroa pre oko 20 godina, a kasnije i kroz divnu knjigu koja se zove "Parazit Reks" mog prijatelja Karla Cimera. Od tada pišem o ovim stvorenjima. Ima malo tema u biologiji koje me više uzbuđuju. Kao da su paraziti omamili moj mozak. Ipak su uvek ubedljivi i predivno sablasni. Kada pišete o parazitima, vaš rečnik prepun je izraza poput "živ proždran" i "iskače iz svog tela." (Smeh)
But there's more to it than that. I'm a writer, and fellow writers in the audience will know that we love stories. Parasites invite us to resist the allure of obvious stories. Their world is one of plot twists and unexpected explanations. Why, for example, does this caterpillar start violently thrashing about when another insect gets close to it and those white cocoons that it seems to be standing guard over? Is it maybe protecting its siblings? No. This caterpillar was attacked by a parasitic wasp which laid eggs inside it. The eggs hatched and the young wasps devoured the caterpillar alive before bursting out of its body. See what I mean? Now, the caterpillar didn't die. Some of the wasps seemed to stay behind and controlled it into defending their siblings which are metamorphosing into adults within those cocoons. This caterpillar is a head-banging zombie bodyguard defending the offspring of the creature that killed it.
Ali tu postoji više od toga. Pisac sam, a kolege pisci iz publike znaju da mi volimo priče. Paraziti nas pozivaju da se odupremo mamcu očiglednih priča. Njihov svet prepun je obrta i neočekivanih objašnjenja. Zašto, na primer, ova gusenica počinje divlje da mlati kada se drugi insekt približi njoj i tim belim čaurama koje ona kao da brani? Da li možda štiti braću i sestre? Ne. Gusenicu je napala osa parazit koja je snela jaja unutar nje. Jaja su se izlegla i mlade ose su proždrale gusenicu dok je živa pre nego što joj izlete iz tela. Vidite o čemu pričam? Gusenica nije uginula. Neke ose kao da zaostaju i kontrolišu je da brani njihovu braću i sestre koje se pretvaraju u odrasle jedinke u tim čaurama. Ova gusenica je zombi čuvar koji mlati glavom i brani potomstvo stvorenja koje ju je ubilo.
(Applause)
(Aplauz)
We have a lot to get through. I only have 13 minutes. (Laughter)
Imamo dosta toga da pređemo. Imam samo 13 minuta. (Smeh)
Now, some of you are probably just desperately clawing for some solace in the idea that these things are oddities of the natural world, that they are outliers, and that point of view is understandable, because by their nature, parasites are quite small and they spend a lot of their time inside the bodies of other things. They're easy to overlook, but that doesn't mean that they aren't important. A few years back, a man called Kevin Lafferty took a group of scientists into three Californian estuaries and they pretty much weighed and dissected and recorded everything they could find, and what they found were parasites in extreme abundance. Especially common were trematodes, tiny worms that specialize in castrating their hosts like this unfortunate snail. Now, a single trematode is tiny, microscopic, but collectively they weighed as much as all the fish in the estuaries and three to nine times more than all the birds. And remember the Gordian worm that I showed you, the cricket thing? One Japanese scientist called Takuya Sato found that in one stream, these things drive so many crickets and grasshoppers into the water that the drowned insects make up some 60 percent of the diet of local trout. Manipulation is not an oddity. It is a critical and common part of the world around us, and scientists have now found hundreds of examples of such manipulators, and more excitingly, they're starting to understand exactly how these creatures control their hosts.
Neki od vas verovatno očajnički traže neku utehu u ideji da su ove stvari neobičnosti prirodnog sveta, da su pojedinačne i to gledište je veoma razumljivo, jer su paraziti po prirodi veoma mali i veliki deo vremena provode unutar tela drugih organizama. Lako je prevideti ih, ali to ne znači da nisu bitni. Pre nekoliko godina, čovek zvani Kevin Laferti poveo je grupu naučnika u tri estuara u Kaliforniji i u principu su merili i disecirali i snimali sve što su našli i otkrili su ogromne količine parazita. Naročito prisutni su bili metilji, crvi koji se specijalizuju za kastriranje svojih domaćina, poput ovog nesrećnog puža. Jedan metilj je sićušan, mikroskopske veličine ali zajedno imaju težinu koliko i sve ribe u estuarima i tri do devet puta više od svih ptica. Sećate li se gordijevog crva kojeg sam vam pokazao, sa cvrčkom? Jedan japanski naučnik, Takuja Soto, otkrio je da u jednom potoku ove stvari vode toliko cvrčaka i skakavaca u vodu da udavljeni insekti čine oko 60% ishrane lokalne pastrmke. Manipulacija nije poseban slučaj. To ključni i čest deo sveta oko nas, i naučnici su sada otkrili stotine primera takvih manipulatora, i što je zanimljivije, počinju da razumevaju tačno kako ova stvorenja kontrolišu svoje domaćine.
And this is one of my favorite examples. This is Ampulex compressa, the emerald cockroach wasp, and it is a truth universally acknowledged that an emerald cockroach wasp in possession of some fertilized eggs must be in want of a cockroach. When she finds one, she stabs it with a stinger that is also a sense organ. This discovery came out three weeks ago. She stabs it with a stinger that is a sense organ equipped with small sensory bumps that allow her to feel the distinctive texture of a roach's brain. So like a person blindly rooting about in a bag, she finds the brain, and she injects it with venom into two very specific clusters of neurons. Israeli scientists Frederic Libersat and Ram Gal found that the venom is a very specific chemical weapon. It doesn't kill the roach, nor does it sedate it. The roach could walk away or fly or run if it chose to, but it doesn't choose to, because the venom nixes its motivation to walk, and only that. The wasp basically un-checks the escape-from-danger box in the roach's operating system, allowing her to lead her helpless victim back to her lair by its antennae like a person walking a dog. And once there, she lays an egg on it, egg hatches, devoured alive, bursts out of body, yadda yadda yadda, you know the drill. (Laughter) (Applause)
Ovo je jedan od mojih omiljenih primera. Ovo je Ampulex compressa, smaragdna osa, i generalno se priznaje da kada smaragdna osa poseduje neka oplođena jaja, ona mora da traži bubašvabu. Kada je nađe, ubada je žaokom koja je takođe čulni organ. Ovo otkriće je nastalo pre tri nedelje. Ubada je žaokom koja je čulni organ sa malim malim čulnim izbočinama koje je joj omogućavaju da oseti posebnu teksturu mozga bubašvabe. Kao osoba koja naslepo opipava torbu, nalazi mozak i u njega ubacuje otrov, u posebna dva skupa neurona. Izraelski naučnici Frederik Libersat i Ram Gal otkrili su da je otrov veoma posebno hemijsko oružje. Ne ubija bubašvabu, niti je omami. Bubašvaba može da odšeta, odleti ili otrči ako želi, ali ona to ne radi, jer joj otrov uništava motivaciju da hoda, i samo to. Osa zapravo isključuje sistem za bežanje od opasnosti u operativnom sistemu bubašvabe, što joj pomaže da bespomoćnu žrtvu odvede u svoje sklonište držeći je za antene kao kada bi neko šetao psa. Kada je tamo, ona položi jaja u nju, jaja se izlegu, pojedu je živu, izleću iz tela, bla bla bla, znate već kako ide. (Smeh) (Aplauz)
Now I would argue that, once stung, the cockroach isn't a roach anymore. It's more of an extension of the wasp, just like the cricket was an extension of the Gordian worm. These hosts won't get to survive or reproduce. They have as much control over their own fates as my car. Once the parasites get in, the hosts don't get a say.
Rekao bih da, kada je ubode osa, bubašvaba nije više bubašvaba. Više je produžetak ose, kao što je cvrčak bio produžetak gordijevog crva. Ovi domaćini neće preživeti i neće se razmnožavati. Nad svojom sudbinom imaju kontrolu koliko i moj auto. Kada paraziti uđu, domaćini se ništa ne pitaju.
Now humans, of course, are no stranger to manipulation. We take drugs to shift the chemistries of our brains and to change our moods, and what are arguments or advertising or big ideas if not an attempt to influence someone else's mind? But our attempts at doing this are crude and blundering compared to the fine-grained specificity of the parasites. Don Draper only wishes he was as elegant and precise as the emerald cockroach wasp. Now, I think this is part of what makes parasites so sinister and so compelling. We place such a premium on our free will and our independence that the prospect of losing those qualities to forces unseen informs many of our deepest societal fears. Orwellian dystopias and shadowy cabals and mind-controlling supervillains -- these are tropes that fill our darkest fiction, but in nature, they happen all the time.
Ljudi su naravno, takođe skloni manipulaciji. Uzimamo lekove da promenimo hemijski sastav svojih mozgova i da promenimo raspoloženje, i šta su argumenti, reklame ili velike ideje ako ne pokušaj da se utiče na nečije mišljenje? Ali naši pokušaji da radimo ovo grubi su i prosti u poređenju sa istančanim pojedinostima parazita. Don Drejper bi voleo da je elegantan i precizan kao smaragdna osa. Mislim da je ovo deo onoga što parazite čini tako zlobnim i ubedljivim. Toliko cenimo našu slobodnu volju i nezavisnost da mogućnost da nam ih oduzmu neviđene sile, budi neke od naših najdubljih društvenih strahova. Orvelovske distopije i sumnjive spletke i zlikovci koji kontrolišu um - ovo su tropi koji ispunjavaju najtamnije delove naše mašte, ali se u prirodi stalno dešavaju.
Which leads me to an obvious and disquieting question: Are there dark, sinister parasites that are influencing our behavior without us knowing about it, besides the NSA? If there are any — (Laughter) (Applause) I've got a red dot on my forehead now, don't I? (Laughter)
Što me dovodi do očiglednog i uznemirujućeg pitanja: Ima li tamnih, zlobnih parazita koji utiču na naše ponašanje a da mi to ne znamo, pored NSA? Ako postoje - (Smeh) (Aplauz) Stoji mi crvena tačka na čelu, zar ne? (Smeh)
If there are any, this is a good candidate for them. This is Toxoplasma gondii, or Toxo, for short, because the terrifying creature always deserves a cute nickname. Toxo infects mammals, a wide variety of mammals, but it can only sexually reproduce in a cat. And scientists like Joanne Webster have shown that if Toxo gets into a rat or a mouse, it turns the rodent into a cat-seeking missile. If the infected rat smells the delightful odor of cat piss, it runs towards the source of the smell rather than the more sensible direction of away. The cat eats the rat. Toxo gets to have sex. It's a classic tale of Eat, Prey, Love. (Laughter) (Applause)
Ako postoje, ovo je dobar kandidat. Ovo je Toxoplasma gondii ili ukratko Tokso, jer zastrašujućem stvorenju uvek pogoduje simpatičan nadimak. Tokso pogađa sisare, veliki broj sisara, ali seksualno može da se razmnožava samo u mačkama. Naučnici poput Džoen Vebster su pokazali da, ako Tokso uđe u pacova ili miša, pretvara glodara u projektil koji traži mačku. Ako inficirani pacov namiriše predivnu aromu mačjeg urina, on trči prema izvoru mirisa umesto smislenijeg pravca koji podrazumeva bežanje. Mačka pojede pacova. Tokso ima seksualni odnos. Klasična priča "Jedi, lovi, voli." (Smeh) (Aplauz)
You're very charitable, generous people. Hi, Elizabeth, I loved your talk.
Vi ste veoma milosrdni i darežljivi ljudi. Zdravo Elizabet, jako mi se dopao tvoj govor.
How does the parasite control its host in this way? We don't really know. We know that Toxo releases an enzyme that makes dopamine, a substance involved in reward and motivation. We know it targets certain parts of a rodent's brain, including those involved in sexual arousal. But how those puzzle pieces fit together is not immediately clear. What is clear is that this thing is a single cell. This has no nervous system. It has no consciousness. It doesn't even have a body. But it's manipulating a mammal? We are mammals. We are more intelligent than a mere rat, to be sure, but our brains have the same basic structure, the same types of cells, the same chemicals running through them, and the same parasites. Estimates vary a lot, but some figures suggest that one in three people around the world have Toxo in their brains. Now typically, this doesn't lead to any overt illness. The parasite holds up in a dormant state for a long period of time. But there's some evidence that those people who are carriers score slightly differently on personality questionnaires than other people, that they have a slightly higher risk of car accidents, and there's some evidence that people with schizophrenia are more likely to be infected. Now, I think this evidence is still inconclusive, and even among Toxo researchers, opinion is divided as to whether the parasite is truly influencing our behavior. But given the widespread nature of such manipulations, it would be completely implausible for humans to be the only species that weren't similarly affected.
Kako parazit kontroliše domaćina na ovaj način? Zaista ne znamo. Znamo da Tokso ispušta enzim koji proizvodi dopamin, supstancu koja ima veze sa nagrađivanjem i motivacijom. Znamo da cilja na određene delove mozga glodara, uključujući i one za seksualno uzbuđenje. Ali kako se ti delići slagalice uklapaju, nije sasvim jasno. Jasno je da je ova stvar jedna ćelija. Nema nervni sistem. Nema svest. Čak nema ni telo. Ali manipuliše sisarom? Mi smo sisari. Sigurno smo inteligentniji od pacova, ali naši mozgovi imaju istu osnovnu strukturu, istu vrstu ćelija, iste hemikalije koje idu kroz njih, i iste parazite. Procene variraju, ali po nekim brojkama, jedna od tri osobe u svetu imaju Tokso u svojim mozgovima. Ovo obično ne vodi ni do kakve bolesti. Parazit stoji u uspavanom stanju dug period vremena. Ali postoje neki dokazi da ti ljudi koji nose parazite imaju pomalo drugačije rezultate na ispitivanjima ličnosti od drugih ljudi, imaju neznatno veći rizik od saobraćajnih nesreća, i postoje neki dokazi da ljudi sa šizofrenijom imaju veću sklonost da se zaraze. Mislim da dokazi još uvek nisu jasni, i čak među istraživačima Toksoa su podeljena mišljenja o tome da li parazit zaista utiče na naše ponašanje. Ali s obzirom na rasprostranjenost takvih manipulacija, bilo bi potpuno neverovatno da ljudi budu jedina vrsta koja nije slično pogođena.
And I think that this capacity to constantly subvert our way of thinking about the world makes parasites amazing. They're constantly inviting us to look at the natural world sideways, and to ask if the behaviors we're seeing, whether they're simple and obvious or baffling and puzzling, are not the results of individuals acting through their own accord but because they are being bent to the control of something else. And while that idea may be disquieting, and while parasites' habits may be very grisly, I think that ability to surprise us makes them as wonderful and as charismatic as any panda or butterfly or dolphin.
Mislim da ovaj kapacitet da stalno podrivaju način na koji mislimo o svetu čini parazite izuzetnim. Stalno nas pozivaju da na prirodni svet gledamo sa strane, i da se pitamo da su li ponašanja koja vidimo jednostavna i očigledna ili zbunjujuća i zagonetna, da nisu posledica pojedinaca koji se ponašaju po svom nahođenju već ih nešto drugo upravlja i kontroliše. Iako je ta ideja možda uznemirujuća, i dok su navike parazita jezive, mislim da ih ta mogućnost da nas iznenade čini divnim i harizmatičnim poput bilo kog pande, leptira ili delfina.
At the end of "On the Origin of Species," Charles Darwin writes about the grandeur of life, and of endless forms most beautiful and most wonderful, and I like to think he could easily have been talking about a tapeworm that makes shrimp sociable or a wasp that takes cockroaches for walks.
Na kraju "Porekla vrsta", Čarls Darvin piše o veličanstvenosti života, i o beskrajnim oblicima, prelepim i predivnim, i mislim da je veoma lako mogao da priča o pantljičari koja čini škampe društvenijim ili osi koja šeta bubašvabe.
But perhaps, that's just a parasite talking.
Ali možda to samo priča parazit.
Thank you.
Hvala vam.
(Applause)
(Aplauz)