Slashdot Mirror
Wasp Larvae Feed on Zombie Roaches
TheUploader writes "The story leaves nothing to embellish: The wasp, Ampulex compressa, has evolved to inject a toxin into a specific part of a roach's brain, turning it into a zombie. The wasp then leads the zombie roach into the wasp's nest, lays eggs inside it, and waits for its young to hatch, who will then go on to do the same to more roaches."
http://loom.corante.com.nyud.net:8090/archives/200 6/02/02/the_wisdom_of_parasites.php
here, hope this can handle slashdot. http://www.palmpowerups.com/priv/mirror.pdf
-------
1. Enjoy your job
2. Make lots of money
3. Work within the law
Choose any two.
"To face death, that's nothing much. But to feel really stupid when you die, well, that would be insufferable."
Incidentally, today is Romero's birthday...
THE LOOM
February 02, 2006 The Wisdom of Parasites
Posted by Carl Zimmer
I collect tales of parasites the way some people collect Star Trek plates. And having filled an entire book with them, I thought I had pretty much collected the whole set. But until now I had somehow missed the gruesome glory that is a wasp named Ampulex compressa.
As an adult, Ampulex compressa seems like your normal wasp, buzzing about and mating. But things get weird when it's time for a female to lay an egg. She finds a cockroach to make her egg's host, and proceeds to deliver two precise stings. The first she delivers to the roach's mid-section, causing its front legs buckle. The brief paralysis caused by the first sting gives the wasp the luxury of time to deliver a more precise sting to the head.
The wasp slips her stinger through the roach's exoskeleton and directly into its brain. She apparently use ssensors along the sides of the stinger to guide it through the brain, a bit like a surgeon snaking his way to an appendix with a laparoscope. She continues to probe the roach's brain until she reaches one particular spot that appears to control the escape reflex. She injects a second venom that influences these neurons in such a way that the escape reflex disappears.
From the outside, the effect is surreal. The wasp does not paralyze the cockroach. In fact, the roach is able to lift up its front legs again and walk. But now it cannot move of its own accord. The wasp takes hold of one of the roach's antennae and leads it--in the words of Israeli scientists who study Ampulex--like a dog on a leash.
The zombie roach crawls where its master leads, which turns out to be the wasp's burrow. The roach creeps obediently into the burrow and sits there quietly, while the wasp plugs up the burrow with pebbles. Now the wasp turns to the roach once more and lays an egg on its underside. The roach does not resist. The egg hatches, and the larva chews a hole in the side of the roach. In it goes.
The larva grows inside the roach, devouring the organs of its host, for about eight days. It is then ready to weave itself a cocoon--which it makes within the roach as well. After four more weeks, the wasp grows to an adult. It breaks out of its cocoon, and out of the roach as well. Seeing a full-grown wasp crawl out of a roach suddenly makes those Alien movies look pretty derivative.
I find this wasp fascinating for a lot of reasons. For one thing, it represents an evolutionary transition. Over and over again, free-living organisms have become parasites, adapting to hosts with exquisite precision. If you consider a full-blown parasite, it can be hard to conceive of how it could have evolved from anything else. Ampulex offers some clues, because it exists in between the free-living and parasitic worlds.
Amuplex is not technically a parasite, but something known as an exoparasitoid. In other words, a free-living adult lays an egg outside a host, and then the larva crawls into the host. One could easily imagine the ancestors of Ampulex as wasps that laid their eggs near dead insects--as some species do today. These corpse-feeding ancestors then evolved into wasps that attacked living hosts. Likewise, it's not hard to envision an Ampulex-like wasp evolving into full-blown parasitoids that inject their eggs directly into their hosts, as many species do today.
And then there's the sting. Ampulex does not want to kill cockroaches. It doesn't even want to paralyze them the way spiders and snakes do, since it is too small to drag a big paralyzed roach into its burrow. So instead it just delicately retools the roach's neural network to take away its motivation. Its venom does more than make roaches zombies. It also alters their metabolism, so that their intake of oxygen drops by a third. The Israeli researchers found that they could also drop oxygen consumption in cockroaches by injecting paralyzing drugs or by removing the neurons that the wasps disable with the
The fungus you refer to is mentioned in this article, which ironically was linked to from a past Slashdot story. They just call it an enslaver fungus, they don't actually name the species they are referring to.
But it sounds like this type of adaptive mechanism is more common than you would think. Quite amazing actually - how on earth would a parasite evolve the right chemical signal to trigger its host to jump into water or perch at the top of a tree? Very bizarre.
Many insects and arachnids paralyze or kill their prey with poison and lay eggs in, on, or near them. This is simply an interesting variation on that.
Conclusion: the Empire squashes the Federation like a bug. Accept it.
I should point out that the fungus in question might actually be a species of Cordyceps rather than Entomophthorales. There's a cool photo of a beetle that was killed by a parasitic fungus at bugguide.net.
Si la vida me da palo, yo la voy a soportar Si la vida me da palo, yo la voy a espabilar
Just for clarification, Romero never made brain eating zombies. His particular breed just ate people alive. (best part of a zombie movie, really, is when they decide to rip someone to pieces. See : Shaun of the Dead, or any of Romero's films)
_ Dead
The brain-eating cliché came from Return of the Living Dead, which had nothing to do with Romero's movie, save for a producer involved, I believe.
To be quite honest, I thought this wasp had stronger horror movie ties to the Alien series, and was probably even a direct influence on Giger's design (or was the Ridley's? I'm not sure who invented the creature's actual properties). I mean, when they hatch, those wasp larvae DO in fact, eat their way out of the roach.
errr, thanks to Wikipedia, a clarification on that Romero bit :
http://en.wikipedia.org/wiki/Return_of_the_Living
- peace
You're thinking of Dicrocoelium dendriticum, the sheep liver fluke. The eggs get passed out in the feces, and are eaten by a snail. The snail sheds a second-stage larvae, which is eaten by an ant. The parasite causes the ant to become negatively geotropic - it climbs up onto the grass - and is eaten by the sheep, where it grows into an adult and starts the whole process over.
FTA:
Amuplex is not technically a parasite, but something known as an exoparasitoid. In other words, a free-living adult lays an egg outside a host, and then the larva crawls into the host. One could easily imagine the ancestors of Ampulex as wasps that laid their eggs near dead insects--as some species do today. These corpse-feeding ancestors then evolved into wasps that attacked living hosts. Likewise, it's not hard to envision an Ampulex-like wasp evolving into full-blown parasitoids that inject their eggs directly into their hosts, as many species do today.
There is much cruelty in the universe, John.
Yeah, we seem to have the tour map.
Mark Twain also saw wasp parasitism in particular as an argument against benevolent design. See, for example, his late sketch "Little Bessie".
how many evolutionary failures must there have been before the first momma wasp hit those particular neurons?
No need to assume "evolutionary failure" in not stinging the right spot. For a handwaving just-so story, just assume the head sting started as a way to kill a roach to ensure a very fresh, plump corpse for the larvae. Then, a slightly less violent sting would sometimes paralyze - but not outright kill - the host, making for even better conditions. And so, gradually, improvements in accuracy and specificity of the venom would make for better and better conditions for the larvae.
The original paper can be found here. It actually dates from 2003. Despite my weak biology background, I found it very readable.
They also describe an interesting middle phase of the wasp attack which was not mentioned in the summary: after the brain injection, the roach furiously "grooms" itself for 30 minutes. They also note that the zombie behavior takes about 30 mins to take hold. Thus there's a possibility that the intense "itch" in the cockroach keeps it in the same place until its escape reflex has been fried.
Well, and if we want to get pedantic, Romero zombies never ate anybody's brains. They mostly went for the guts. It was "Return of the Living Dead," the comedy/horror take-off on the Romero films, that brought in all the brain-eating.
Breakfast served all day!
Of course, it can't be disproven either. I find it hilarious when people point this out, because science, by definition, is experimental study of the natural world. When you leave the realm of the natural world, it isn't science anymore. That doesn't mean there isn't anything outside of the natural world, it just means that we can't come to any conclusions about it scientifically.
As a biologist (molecular genetics), I would say that this is the side of evolution people in the field don't talk about. I don't think I've ever read any papers (doesn't mean it doesn't exist) in which a serious study has been taken to answer the question of how evolution can be a CREATIVE process. Here's what I mean:
Microevolution (the DNA mutations and their inheritance by the progeny) occurs all the time, I think we can all agree on this. Macroevolution and speciation on the other hand, is a very hand wavy thing. In macroevolution, new structures or functions are derived from an ancestor. All the widely cited example of evolution, may it be Darwin's finches or the peppered moths are variation of existing structures. In terms of DNA mutations, this may only take a few changes in the actual DNA sequences which regulate the expression (or the turning on) of certain genes. The probability of these mutation events is already pretty low, but one can imagine this happening.
However, the question in the original post of how single base-pair (bp) mutations can lead to an organism not having a given ability at all to having an ability to control the roaches involves invoking evolution as having a CREATIVE force. As an excercise, let's just imagine that we are trying to create a brand new smallish 100 amino acid neuro-peptide that can control the roach by evolution. If you start with some random DNA sequence and try to evolve a 300 bps (3 bps/aa). You will end up with a probability of 1/4^300 = 2.4x10^-181 chance of evolving that (ok it'll be a little higher because 1/4 of the DNA will already be the one you want). That's a pretty small probability in anyone's book. You also have to account for the fact that while you are trying create this protein, other things are getting mutated in your genome and probably killing off the larvae before they have a chance to pass down their genes. Since you have not created a fully functional gene yet, there is no selective advantage for this specific gene locus, and the half-evolved gene is just being carried along in the population at a very low frequency. This means that it is very easily lost in the population and you have to start over trying to create your gene again.
This is just for evolving the neuro-peptide. For the gene to function properly, you NEED regulatory DNA sequences that control the protein to be expressed in the right place (ie. the stinger). There are also a lot of other things that the protein needs to be delivered to the roaches' brain (like the entire secretory pathway). But let's not go into that.
So I hope one can see, that the probability for all these events to occur is very very low, I would say a mathematical improbablity. And this is just for ONE protein to function properly!
Don't get me wrong, I stare a lot at DNA sequence data, and some things make a convincing case for evolution. But again, it's just microevolution. For creation of new structures and functions, and speciation, a lot more is needed. Speciation is not an observable event, and neither is the formation of new structures. Before we go and hail evolution as the new dogma of the modern man, we need to take this into consideration. And teach it like it is: if the enterprise of science is the search for "the truth" we need to be open and admit the assumptions and the caveats in our hypothesis. And that's what macro-evolution is: an hypothesis.
Likewise, the grandparent's argument implies there IS a reason for suffering. Western religions are populated by such a bunch of crybaby four year olds.
Suffering just is. There's always something. The buddha noticed it two hundred years BC and noticed it's inescapable. But in the east, they don't assume some single creature is doing it deliberately; after all, it's not like it really matters.
He also noticed WE make the suffering worse but sitting there bitching about how wrong and unfair it all is, and going "Why? Why? Why?".
Thirdly he noticed we can make it quite a bit better.
Last he said the way to make it better is to quit wishing for things to be different. Once we give up these desires, suffering vanishes.
Westerners should think about these ideas more. At least it would be quieter.
O~ Him that studies revenge keeps his own wounds green. -- Francis Bacon
because Loving and Suffering are two subjective statements, and is strictly relative those who subscribe to those two ideas
Yeah, right. Tell that to the millions who die from unpleasant parasitic diseases each year - "Your suffering is only subjective".