Parasite turns ants into juicy berries to entice hungry birds

Here's a freaky Parasite Rex moment for you: an Amazonian nematode makes infected ants swell up to resemble bright red berries, which entices birds to eat them and then spread the nematodes around the jungle:
This bizarre lifecycle of a parasitic nematode, or roundworm, plays out in the high canopy of tropical forests ranging from Central America to the lowland Amazon, according to Robert Dudley, a professor of integrative biology at the University of California, Berkeley.

"It's just crazy that something as dumb as a nematode can manipulate its host's exterior morphology and behavior in ways sufficient to convince a clever bird to facilitate transmission of the nematode," Dudley said.

"It's phenomenal that these nematodes actually turn the ants bright red, and that they look so much like the fruits in the forest canopy," said co-author Stephen P. Yanoviak, an insect ecologist and assistant professor of biology at the University of Arkansas at Little Rock, who noted that numerous tropical plants produce small red, orange and pink berries. "When you see them in the sunlight, it's remarkable."



  1. Yep, you don’t even have to be in the tropical forest for this sort of thing. There’s a parasite that uses ants as an intermediate host between gastropods and sheep. The infected ants climb on up to the top of a blade of grass and wait. They’ll do this every darn day until a grazing sheep eats them.

    And wasn’t i just reading about parasites that made mice so crazy with courage that they challenged cats? Same kind of deal.

    Deepy, I think you might be on to something. I think a similar parasite, one that infects humans, could explain a lot about why folks in the USA voted the way they did these last two presidential elections.

  2. i so hate it when folks (scientists!) write this way about animal traits, constantly attributing intentionality/agency.
    nematodes having an effect on their hosts is “crazy” only if you portray it using such inappropriate terms as “dumb” vs. “clever”, “manipulate”, “sufficient to convince”, etc.

    what’s in any way “phenomenal” about the presence of an extraneous organism effecting the colour of its host? if i’m not mistaken, that’s just chemistry.

    sure, it’s fun to see nature’s complexity, to see the kinds of systems that have evolved, but if scientists continue to speak so misleadingly, it’s a small wonder that so many people don’t “get” the basics of evolution.

  3. I’m sure the intelligent design folks would see this as an example of a relationship in nature that almost seems too perfect to happen by chance. I just think it’s an example of a very complex feedback loop, one that must have taken a while to become established and supported. I’m wondering why, nature will suport something that is benificial for the nematode, but not the ant? Why hasn’t the ant evolved to either kill the worm or counter the effects? Why has nature used the worm to kill the ant? Too many ants? And how does this “knowledge” get transmitted?

  4. @6 Jeff

    In fact nature isn’t “supporting” any plight or strategy over any other. its more like this:
    a parasite natually infects an ant and produces some effect (swollen abdomen, say). some birds (who like berries) mistake swollen ants for berries -gobble- and so the birds (rather than nature) are supporting the parasites’ strategy.
    eventually, over many generations, the birds will pick the ant/parasite that look most like red-forest-berries because that’s what birds like. so natural selection will ensure (not by knowledge or intention) that eventually the parasite makes very specific berry-looking ants.
    this is not because nature chose the parasite over the ant, or the bird over either, but because the bird has picked the most appealing-looking ants over and over for generations, and natural selection has ‘obliged’ to make the parasites effect more berry-like (because of the feedback loop between supply and demand) as birds pick the most-berry-looking of each new generation..

  5. Arkizzle, birds are part of nature (of course). So, nature is supporting something (ant control, and bird feeding). I think there’s more to evolution than meets the eye. Saying it’s all Evolution seems too simplistic to me.

  6. Jeff, I expect the ants are doing their best to fight off the nematode. It’s a bit analogous to sickness in humans– “why would natural selection lead to a virus infecting our cells, using their machinery to make tons of new virions, and killing the cells in its quest to reproduce? Why don’t our cells fight back?” Well, the cells do fight back; we have an immune system that does its best to kill the virus or ameliorate its attack. The ant’s immune system tries to kill the nematode at some point during its invasion, but once it’s really far alonge, the ant has lost and becomes birdfood.

    Thank you, Progosk, for catching the intelligence thing. That was going to bug me all day if I didn’t comment. It doesn’t take intelligence to produce complexity.

  7. it’s a pet peeve of mine. how often in explanations of evolution do you hear about animals adapting? they don’t – they are subject to selection.

    by not getting the basics across (mainly: 1. how radical a process natural selection is 2. the timescope – millions of years is an *incredible* lot) evolution-misunderstanding is absolutely the norm in most circles.

    i’m somewhat surprised this aspect isn’t noticed/stigmatised more often.

  8. @Jeff

    I’m sorry, but the way you are saying it, implies that nature is making a conscious decision in the birds favour. It isn’t.

    Birds are indeed a part of nature, but so are the ants and the parasites, so why pick the birds as representative of natures “choice”? There is no choice, just results (cause and effect). At other times the ants win over other participants of nature such as leaves and aphids. There is no choice being made.

    If I go out and pick an orange from the tree, you would hardly say that nature chose me to have the orange. But through millenia of change (and my species’ responses to a changing environment), I stand tall enough to reach the fruit, I have an innate desire to ingest it’s sugary goodness and I have the mental capacity to walk to the tree and harvest what I need. Nature isn’t choosing me to ‘win’ in the battle between me and the tree, evolution has ‘given’ us both strategies to survive and we have both used them (the tree’s seeds will probably be spread better than gravity alone can provide).

    And you are right, saying “It’s all evolution” is FAR too simplistic, and I certainly didn’t say it. That three-word explanation for the entire complexities of our planets eco systems explains nothing at all.. Nature is entirely complicated.

  9. it’s a pet peeve of mine. how often in explanations of evolution do you hear about animals adapting? they don’t – they are subject to selection.

    by not getting the basics across (mainly: 1. how radical a process natural selection is 2. the timescope – millions of years is an *incredible* lot) evolution-misunderstanding is absolutely the norm in most circles.

    i’m somewhat surprised this aspect isn’t noticed/stigmatised more often.

  10. #3: You are correct: The first page of Daniel Dennett’s book “Breaking the Spell: Religion as a Natural Phenomenon” describes how the “lancet flake” can take control of an ant’s brain, driving it to climb upward, to the tops of blades of grass where it is more likely to be eaten and the lancet flake can complete its repoduction within the eating animal’s stomach.

    And yes, fundamentalism, whether it be in the name of a God, or a leader (Hitler, Lenin, Mao), or a God *and* his “annointed leader” (God and GWB, or, God forbid, God and Huckabee), has a similar corrosive effect on the minds of people.

  11. 15 posts until Godwin;s, which isn’t bad.

    Not to defend the scientists choice of “crazy” and dumb”, as those words do serve to help alienate people from understanding evolution, I think its fair to say that this seems like an unusual process, and the scientist was naturally excited, as scientists can be. I’m thinking the word choice was not ignorance so much as the ability to still be fascinated about nature, even when understanding the whole process as well as a scientist can.

  12. I’m actually more intrigued by the ants they were studying before they found the berry-butts– the ones that fall off a tree and glide back to the trunk so they don’t have to walk back. Is the gliding the result of random flailing, like the run-and-tumble of bacterial chemotaxis? Do ants hit the tree more than randomly? Is it reflex or driven by muscles rather than nerves?

  13. Diatryma said, “It doesn’t take intelligence to produce complexity.”

    Maybe. Complexity, reality as you know it, may indeed rely on intelligence. At least in the Beginning. Or does science now perport to know what happened before the beginning of this Universe? It doesn’t, and I know that, and I also know that natural selection may not be the –only– answer.

  14. ‘by not getting the basics across (mainly: 1. how radical a process natural selection is 2. the timescope – millions of years is an *incredible* lot) evolution-misunderstanding is absolutely the norm in most circles. i’m somewhat surprised this aspect isn’t noticed/stigmatised more often.’

    It’s true. Even avowed “anti-creationist” people usually don’t understand the mechanics of evolution.

    Part of the problem is that no biologist makes mistakes about the word “adapt”– it’s simply short-hand to refer to the population changes that result from selection. But when the word ‘adapt’ gets used offhand in publicity material, along with the personifications, it just hurts the greater discourse. In the same way, ‘crazy’ is a kind of short-hand for “i marvel at the dialectics that we find in the natural world”.

    With regards to “why haven’t ants been given some counter-advantage”, the answer seems to be: 1) We’re only at a single point in time; give it time 2) Like the Dodo, some species lose. When the fat lady sings it could be the ants or the germy worms.

    “Nature’s choice”, in specific reference to two interacting species, is simply a poetic way of saying “well, right now in the grand scheme of things, X is really taking Y for a ride, not the other way around.” Anyway for all we know in a few generations the worm could be extinct.

    Jeff: “Natural selection” isn’t the ‘only’ answer to anything. Nobody claims that. It’s only one component of evolution as currently understood. Natural selection wouldn’t exist if there wasn’t inherent pre-existing variation and re-variation for it to operate on. The issue of what happened at “the beginning” is totally irrelevant– we have evidence of, and can see for ourselves, processes that have taken place in local time. Only mystical ignoramuses claim to know what happened “before this universe”– not scientists. It’s not a practical question so intelligent practically-minded people don’t bother with it.

  15. “It’s just crazy that something as dumb as a nematode . . .”

    Well, evolution is “dumb”– there’s no thought involved (unless you consider “god” as the spirit beneath all things, or something). It’s like finding a stone that looks like a bird– it wasn’t MADE, the natural forces just turned it out that way. The nematode is no weirder than you or I or your mother. This is the great marvel of the process of evolution, and why it makes such perfect sense. Those who can’t understand it are simple-minded or willfully ignorant.

    Of course, if you see water stain on your wall that looks like the Virgin Mary, well. . . that’s different.

  16. I read the article and wanted to post my gripe about the bad habit of authors/scientists portraying natural selection as conscience manipulative intelligence as soon as I could, but I see that others have beat me to the punch. But of course they have manipulated BoingBoing and my work schedule to allow them first access.

  17. Jeff- your concept of “before” the universe is meaningless, since there was no time for such a phenomenon as “before” to exist. And you can’t claim that God is outside the universe- for if that is true, either the universe is not the universe or God is not God.

    Natural selection can be and has been directly observed- surely a creator who sets up a self-replicating system capable of endless complexity without interference is more perfect than one who has to perform a miracle every time two moths have sex?

    “Science” does not “claim” to have *any* answers- it is not a monolith but a process of constant enquiry whose primary goal is to prove itself wrong whenever possible, in the hopes of eventually achieving understanding rather than “simple” faith.

  18. Pipenta says a parasite that affects humans might explain the last two presidential elections; allow me to present toxoplasmosis, which scientists have theorized has an effect on both individual and mass human behavior. A third of the world’s population is estimated to host this parasite, including the those of us in the developed world.

    For the individual, it makes women friendlier and better groomed but men the opposite; increases the ratio of boys to girls born, and increases the neuroticism of all. (Also makes the hosts fonder of cats, an essential part of the parasite’s life cycle.)

    In addition, says Kevin Lafferty, a USGS scientist at UC Santa Barbara, “The geographic variation in the latent prevalence of Toxoplasma gondii may explain a substantial proportion of human population differences we see in cultural aspects that relate to ego, money, material possessions, work and rules.”

    Just wanted to point out that we are part of the cycle too, and don’t even realize it.

  19. To all those who are getting their panties in a twist about scientists using metaphors, have any of you read their actual published scientific papers? Stylistically these tend to be dry; third-person, passive voice and very carefully selected wording.

    However, when the same scientists talk to a general audience, they take a more relaxed approach. They might even throw in a few generalities and metaphors to make the subject more accessible to regular folks who don’t spend much time reading scientific literature and might nod off if they did.

    But hey, this is pretty nifty stuff. And if you don’t find it phenomenal, you might just might need to get out in the sunshine and walk around and breathe some fresh air and really start to dig the universe more.

    (#15, I recently watched both of Dennett’s TED lectures and heard him mention these ants. But I’d stumbled across them before in an entomology class and in a couple of other books.)

  20. Pretty good threat. Thank you, Progosk, for voicing my initial thoughts on this.

    I presume quite a few people in this discussion have already read the book “The Selfish Gene” by Dawkins, if not, I highly recommend it to anyone who would like to find out more about this subject matter.

  21. Dawkins is good with explaining how nature seems to work. But he needs to make such a point that NO diety is required in this process. He’s just stating the obvious, which relates just as well to science as spirit: Some times you have to work hard to find the answers, be they scientific or spiritual. If you want to a Higgs boson you have to work hard. At least that’s my theory. I think people who have worked toward God and who have a meaningful belief in God that is derived from meaningful experience, are qualified to talk about it. And anyone else is just not an expert. I wouldn’t trust anyone but an expert to give me important advice. It’s a complex subject, demanding attention to details. Only those who know God (in some way) can talk about the subject with any meaning. Can you know what it’s like to have a baby if you’ve never had one? The same thing is true for those who have had a Satori, or Revelation, or an Epiphany. And guess what, some of –these– people are well known and prominant scientists. You can have both science and God. The two are not mutually exclusive.

  22. Jeff,

    I’m a yogi. At the heart of yoga is the idea that consciousness is the fundamental substance from which time, space, energy and matter devolve. Is it a religious belief? There’s nothing about it that would offend a really smart physicist. Spirituality and physics start to come pretty close together as you dig deeper into either one.

  23. Infected ants, normally black, develop a bright red abdomen, called a gaster, and tend to hold it in an elevated position, an alarm posture in ants. The ants also get sluggish, and the gaster is easily broken off, making it easy for birds to pluck.

    Just imagine. You’re an ant, walking along, minding your own business, when you accidentally bump into one of your fellow ants. And her butt promptly falls off … :P

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