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.
Stado divljih zvijeri, plova ribe jato ptica. Mnoge životinje se okupljaju u velike skupine koje su među najdivnijim prizorima u prirodnom svijetu. Ali zašto se ove grupe formiraju? Uobičajeni odgovori uključuju stvari kao traženje sigurnosti u velikim brojkama ili lov u čoporu ili skupljanje kako bi se parili ili razmnožavali i sva ova objašnjenja, iako su često točna, prave veliku pretpostavku vezanu uz ponašanje životinja, da životinje imaju kontrolu nad vlastitim akcijama, da imaju kontrolu nad svojim tijelima. Što često nije slučaj.
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 Artemia, mali škamp. Vjerojatno vam je poznatiji kao morski majmunčić. Malen je, i uobičajeno živi sam, ali se može skupiti u ove velike crvene rojeve koji se prostiru metrima, te se oni formiraju zbog parazita. Ovi škampi zaraženi su trakavicom. Trakavica je zapravo dugo, živuće crijevo sa genitalijama na jednom kraju i ustima s kukicama na drugom. Kao novinar slobodnjak, suosjećam. (Smijeh) Trakavica uzima hranjive tvari iz Artemiina tijela, ali također čini i druge stvari. Kastrira ih, mijenja im boju iz prozirne u žarko crvenu, tjera ih da dulje žive, i kako je biolog Nicolas Rode utvrdio, tjera ih da plivaju u grupi. Zašto? Jer trakavica, kao i mnogi drugi paraziti ima kompliciran životni ciklus koji uključuje puno različitih domaćina. Škampi su samo jedan korak na tom putovanju. Njihovo krajnje odredište je ovo, veliki flamingo. Samo se u flamingu može razmnožavati trakavica, te kako bi došla tamo, manipulira svog škampa domaćina u formiranje ovih urotničkih obojenih rojeva koji su lakši za uočavanje flamingu kako bi ih pojeo, i to je tajna Artemia roja. Nisu druželjubivi svojom voljom, nego zato što ih kontroliraju. To nije sigurnost u brojkama. To je čista suprotnost. Trakavica otima njihove mozgove i tijela, pretvarajući ih u vozila kojima dolaze 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?
I evo još jednog primjera parazitske manipulacije. Ovo je cvrčak samoubojica. Ovaj cvrčak progutao je larvu Gordijskog crva, ili crva konjske dlake. Crv je narastao do svoje odrasle veličine u njemu, ali treba doći u vodu kako bi se pario, i to čini tako što ispušta proteine koji utječu na cvrčkov mozak, uzrokujući neočekivano ponašanje. Kada se cvrčak približi vodi, kao što je bazen, on uskoči i utopi se, i crv izmigolji van iz svog suicidalnog leša. Cvrčci su zaista prostrani. Tko 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)
Trakavica i Gordijski crv nisu usamljeni. Oni su dio čitave kavalkade parazita koji kontroliraju um, gljivica, virusa, crva i insekata i drugih koji se specijaliziraju u rušenju i premošćivanju volje njihovih domaćina. Prvi puta sam saznao za ovakav način života kroz "Iskušenja života" Davida Attenborougha prije dvadesetak godina, i onda kasnije kroz predivnu knjigu naziva "Parazit Rex" moga prijatelja Carl Zimmera. I od tada pišem o ovim bićima. Malo tema u biologiji me više zaokuplja. To je kao da su paraziti premostili moj vlastiti mozak. Jer nakon svega oni su uvijek neodoljivi i divno jezivi. Kada pišete o parazitima, vaš riječnik vrvi frazama kao što su "živ pojeden" i "prsne iz svog tijela." (Smijeh)
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 ima više u tome od navedenog. Ja sam pisac, i ostali pisci u publici znaju da svi mi volimo priče. Paraziti nas pozivaju da se odupremo privlačnosti očitih priča. Njihov svijet je svijet pun zapleta radnje i neočekivanih objašnjenja. Zašto, na primjer, ova gusjenica započne s nasilnim bacakanjem kada joj se približi drugi insekt i bijelim ličinkama koje izgledaju kao da ih čuva? Štiti li možda svoju braću? Ne. Ova je gusjenica napadnuta od strane parazitske ose koja je u nju položila jaja. Jaja su se izlegla i mlade ose proždrle su gusjenicu živu prije nego su se probile van iz njenog tijela. Vidite što mislim? Sad, gusjenica nije umrla. Neke od osa su očito ostale i kontrolirale ju da brani njihovu braću koja su prolazila kroz metamorfozu u odrasle jedinke u tim ličinkama. Ova gusjenica je zombi čuvar koji mlati glavom braneći potomke bića koje ga je ubilo.
(Applause)
(Pljesak)
We have a lot to get through. I only have 13 minutes. (Laughter)
Imamo puno toga za proći. Imam samo 13 minuta. (Smijeh)
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.
Sad, neki od vas vjerojatno očajnički traže neku utjehu u ideji da su ove stvari samo nepravilnosti prirodnog svijeta, da su to rijetki slučajevi, i takav pogled je razumljiv, jer po prirodi, paraziti su poprilično mali i provode puno svog vremena unutar tijela drugih stvari. Lako ih je previdjeti, ali to ne znači da nisu važni. Prije nekoliko godina, čovjek imena Kevin Lafferty poveo je grupu znanstvenika na tri Kalifornijska estuarija i vagali su, razrezali i zabilježili sve što su mogli naći, i ono što su pronašli bili su paraziti u ekstremno velikim brojkama, Naročito uobičajeni bili su trematodi, maleni crvi koji se specijaliziraju za kastraciju svojih domaćina kao ovog nesretnog puža. Sad, jedna trematoda je minijaturna, mikroskopska, ali zajedno težile su kao sve ribe u estuarijima i od tri do devet puta više nego sve ptice. I sjećate se Gordijskog crva kojeg sam vam pokazao, stvar sa cvrčkom? Jedan Japanski znanstvenik imena Takuya Saro pronašao je da u jednom potoku, ove stvari tjeraju toliko cvrčaka i skakavaca na utapanje u vodi da utopljeni insekti čine oko 60 posto ishrane lokalnih pastrva. Manipulacija nije nešto čudno. To je kritični i uobičajeni dio svijeta oko nas, i znanstvenici su našli stotine primjera takve manipulacije, i što je još uzbudljivije, počinju razumjevati točno kako ova bića kontroliraju 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)
I ovo je jedan od meni najdražih primjera. Ovo je Ampulex compressa, smaragdna žoharova osa, i to je istina koja je univerzalno prihvaćena, da osa u posjedu oplođenih jaja mora biti u potrazi za žoharom. Kada ga pronađe, ubode ga žalcem koji je također i taktilni organ. Ovo otkriće dogodilo se prije otprilike tri tjedna. Ubode ga žalcem koji je taktilni organ opremljen malenim senzorskim kvrgama koje joj dozvoljavaju da ispipa teksture žoharova mozga. Kao što osoba naslijepo kopa po torbi, ona pronalazi mozak, i ubrizgava mu otrov u dva vrlo specifična klastera neurona. Izraelski znanstvenici Frederic Libersat i Ram Gal pronašli su da je otrov posebna vrsta kemijskog oružja. On ne ubija žohara, niti ga omamljuje. Žohar bi mogao odšetati ili odletjeti ili pobjeći ako bi to odlučio, no ne odlučuje to, jer mu otrov poništava motivaciju za hodanjem, i čini samo to. Osa u osnovi odznačuje kućicu za bježanje od opasnosti u operacijskom sustavu žohara, dozvoljavajući joj da vodi svoju bespomoćnu žrtvu natrag u svoju jazbinu za njenu antenu kao što osoba šeta psa. I kad je tamo, polaže jaje na njega, jaje se izlegne, proždire ga živog, probije se iz tijela, bla bla bla, znate kako to ide. (Smijeh) (Pljesak)
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.
Sad, razmotrio bih stav, da kada je uboden, žohar više nije žohar. Više je produžetak ose, baš kao što je cvrčak produžetak Gordijskog crva. Ovi domaćini neće preživjeti ili se reproducirati. Imaju onoliko kontrole nad svojom sudbinom koliko i moj automobil. Jednom kada paraziti uđu, domaćini nemaju pravo glasa.
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.
Ljudima, naravno, nije nepoznata manipulacija. Uzimamo lijekove kako bismo pomaknuli kemiju našeg mozga i promijenili svoje raspoloženje, i što su argumenti ili oglašavanje ili velike ideje ako ne pokušaj da utječemo na nečiji um? Ali naš pokušaj da to učinimo je jednostavan i nepromišljen u usporedbi sa fino vezenom specifičnošću parazita. Don Draper samo želi biti elegantan i precizan kao smaragdna žoharova osa. Sad, mislim da je ovo dio onoga što čini parazite tako zlokobnima i zaokupljajućima. Stavljamo takvu važnost na našu slobodnu volju i našu neovisnost da mogućnost gubitka tih kvaliteta od strane neviđenih sila potiče mnoge od naših najdubljih društvenih strahova. Orwellovska distopija i sjenovita kabala i super-zločinci koji kontroliraju umove -- ovo su stvari koje ispunjavaju našu najmračniju fikciju, ali u prirodi, to se događa cijelo vrijeme.
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 vodi do očitog i uznemirujućeg pitanja: Postoje li mračni, zlokobni paraziti koji utječu na naše ponašanje bez da mi znamo za to, osim NSA? Ako ima -- (Smijeh)(Pljesak) Imam crvenu točku na čelu sad, zar ne? (Smijeh)
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 ih ima, ovo je dobar kandidat za njih. Ovo je Toxoplasma gondii, ili skraćeno Toxo, zato što zastrašujuća bića uvijek zaslužuju simpatični nadimak. Toxo može zaraziti sisavce, širok raspon sisavaca, ali se može seksualno razmnožavati jedino u mački. I znanstvenici kao što je Joanne Webster pokazali su nam da ako se Toxo nastani u mišu ili štakoru, on pretvori glodavca u raketu koja traži mačke. Ako zaraženi štakor namiriše divni miris mačje mokraće, trči prema izvoru mirisa rađe nego u razumnom drugom smjeru. Mačka pojede štakora. Toxo se može seksati. To je klasična priča Jedi, lovi, voli. (Smijeh)(Pljesak)
You're very charitable, generous people. Hi, Elizabeth, I loved your talk.
Vi ste vrlo velikodušni, dobrotvorni ljudi. Hej, Elizabeth, svidio mi se 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 kontrolira domaćina na ovaj način? Zaista ne znamo. Znamo da Toxo ispušta enzim koji stvara dopamin, supstancu koja je povezana sa nagrađivanjem i motivacijom. Znamo da cilja određene dijelove žoharova mozga, ukljućujući i one koji su povezani sa seksualnim uzbuđenjem. Ali kako se ovi dijelovi slagalice slažu nije odmah jasno. Jasno je da je ova stvar jedna ćelija. Ovo nema živčani sustav. Nema svijest. Nema čak ni tijelo. Ali manipulira sisavcem? Mi smo sisavci. Mi smo inteligentniji od štakora, to je sigurno, ali naš mozak ima istu osnovnu strukturu, iste vrste stanica, iste kemikalije koje teku kroz njih, i iste parazite. Procjene variraju, ali neke brojke sugeriraju da jedna od tri osobe u svijetu ima Toxo u svom mozgu. Najčešće, ovo ne vodi u neke očite bolesti. Parazit ostaje u latentnom stanju duga vremenska razdoblja. Ali postoje dokazi da ljudi koji su nositelji imaju malo drugačije rezultate na upitnicima ličnosti nego drugi ljudi, da imaju nešto viši rizik od automobilskih nesreća, i postoje neki dokazi da su ljudi koji imaju šizofreniju ćešće zaraženi. Vjerujem da su ovi dokazi još nepotpuni, čak među istraživačima Toxo-a, mišljenja su podijeljena oko toga može li parazit zaista utjecati na naše ponašanje. Ali zbog raširene prirode ovakvih manipulacija bilo bi potpuno nevjerojatno da su ljudi jedina vrsta na koju nemaju sličan utjecaj.
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.
I mislim da ovaj kapacitet da stalno mijenjaju naš način razmišljanja o svijetu čini parazite zadivljujućima. Stalno nas pozivaju da gledamo svijet postrance, i da se pitamo jesu li ponašanja koja vidimo jednostavna i očita ili zbunjujuća i složena, nisu rezultat individualaca koji djeluju po vlastitom nahođenju nego zato što se povijaju kontroli nečeg drugog. I iako je ta ideja uznemirjuća, iako su navike parazita vrlo grozne, mislim da je mogućnost da nas iznenade ono što ih čini divnima i karizmatičnima poput bilo koje 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 "O porijeklu vrsta," Charles Darwin piše o veličanstvenosti života, i o beskrajnim predivnim oblicima i najdivnijim, i volio bih misliti da je lako mogao pričati o trakavici koja čini škamp društvenim ili osi koja vodi žohare u šetnju.
But perhaps, that's just a parasite talking.
Ali možda, možda je to samo parazit koji progovara iz mene.
Thank you.
Hvala vam.
(Applause)
(Pljesak)