Back to: Rinse, Drain, Spin ... more Laundry! | Forward to: Commercial interlude


(I'm off to London for the weekend so will be scarce around here until Tuesday.)

Parasites. By some estimates, up to 75% of identified species are actually parasites of some kind, feeding directly on other organisms. Predators also feed on other organisms. The difference is that predators kill then eat their targets; parasites may damage their host but don't usually kill them directly. There's a sliding scale of lethality. Outright lethal parasitism such as Ophiocordyceps unilateralis or parasitoid wasps do indeed kill their hosts. Others may not kill their hosts but prevent them from reproducing in order to divert the host organism's metabolic surplus towards the castrating parasite. But successful parasites don't kill their hosts, they may even help them: look at the role human gut bacteria play in fermenting undigested carbohydrates into more easily absorbed forms. The most successful parasites become symbiotes—in return for nutrients and shelter they contribute to the host organism's survival. By far the most successful are the endocellular symbionts such as mitochondria, without which complex eukaryotic organisms (from amoebae to human beings) wouldn't exist. It's parasites all the way down, too: some parasites are themselves parasitized by so-called hyperparasites.

Anyway, my starter question is this: what is your favourite parasite? (And why?)

ADMINISTRATIVE NOTE: Ha ha, very funny, no: congressmen and estate agents are not parasitic species, whatever one may think of their niche. I'm deleting all suggestions of human beings. Stick to wildlife. And hey, why no plants yet?



Our cats.

Oh come on, this is the internet.

More seriously, at what stage does predation become parasitism?


[ DELETED BY MODERATOR - human specialities disallowed ]


Toxoplasma gondii. Gives mice the courage to stand up to cats. In humans, makes men act macho and women act sexy. No country with a low rate of Toxoplasma infection has ever won a World Cup.


Obvious answer, but artificial intelligence? At the moment it's too weak to predate, but like parasites, hopefully it will advance to become symbiotic.

Therefore the robots won't take over, they'll just continue to appear to be increasingly sophisticated tools for humans until we're like bacteria in their stomachs...

Oh, you might have had that idea already.


"Wake me when robot wives become cheap and effective."


Wolbachia is pretty cool. Very successful parasite.


[ DELETED BY MODERATOR - human specialities disallowed ]


Will you've doing any public appearances/pub appearances whilst in London or is this a personal trip? Would love to say hi and buy you a beer if it's the former.


Oh and as for fungus who wouldn't go for Ophiocordyceps unilateralis? It's not called the ant-zombie fungus because it's boring :p


[ DELETED BY MODERATOR - human specialities disallowed ]


[ DELETED BY MODERATOR - human specialities disallowed ]


I don't really have a parasite, though malaria gets some coolness points for having seven life stages.

However, I've been wondering if there's any sf which includes a sympathetic version of the viewpoint of intelligent parasites.

Viewpoint herbivores are rare enough-- offhand, all I can think of is Watership Down and Niven's Puppeteers.


There were the organisms in the Futurama episode "Parasites Lost" who occupied Fry and undertook some major improvements. They may be my favourite parasites of all time.


[ DELETED BY MODERATOR - human specialities disallowed ]


I was also going to go with Toxoplasma gondii, but somebody beat me to it. Your most recent Laundry novel references another favourite of mine, for sheer creepiness. The larvae of the Tarantuala Hawk Wasp, while not technically a parasite, deserves a mention. The wasps hunts tarantualas!!!

I will have to go with with the male deepsea anglerfish. I mean, the male becomes effectively a parasite on the female, in order to mate. Isn't that both cool and weird - the lengths some species will go to, to get laid...


Viruses, especially those with reasonably stable latent phases.

Varicella zoster (chickenpox/shingles) is a pretty good example.


H. Sapiens. I'm looking forward to symbiosis with a cow for supper.


The correct answer is "The Corporation" right? At least if I say that it'll promote me and work in symbiosis with me rather than killing me young.


Yeah; I'd say that the domestic shorthair (any breed) qualifies, and as a further SF link, especially if it's called after one of the members of the Manhattan Project, or is called "Zazzles".


[ DELETED BY MODERATOR - human specialities disallowed ]


Personal trip. (Friends' wedding.)


You want stable latent phases? How about human endogenous retroviruses (HERVs)? Retroviruses so successful that they've spliced themselves into our genome on a permanent basis, and only come out to play once in a blue moon?


Cats are clearly predators; arguably, they're not parasites on humans -- they moved in when we began to stockpile grain, because grain stockpiles attract self-propelled furry cat-food (rodents). So they occupied an opportunistic behavioural symbiosis niche from the bronze age onwards -- our behavioral quirk is favourable to their predation pattern which in turn makes life easier for us.


Can I say Zynga? It's piggy backed on Facebook and takes advantage of Facebook members.

Biologically, I must go with the parasitic fungi that change the behavior of ants do they climb high allowing the fungus to sporulate. I really need to re-read Parasite Rex.


You didn't follow the links in the original article, did you?


Mistletoe. And I know of an opportunistic maple tree that is growing out of a crack in the bark of an Ash tree.


When I recall what Tabitha did for us, emotionally, I am inclined to class cats as symbiotes. And since the cats who predate on mice are also getting food and shelter from Humans I would say they have Symbiosis well sorted. Might they even be behind agriculture?

You do not grieve over parasites.


I suppose there are many elements of Symbiosis with any domestic animal. Horses and cattle do quite well out of humans. And they are different because of us.


Cymothoa exigua is pretty cool. It hooks onto fish tongues, extracts the blood from the tongue causing it to fall off, and then becomes a functional replacement tongue! Apparently, this doesn't harm the fish, and it can use its new fish-tongue just like the old one.


Interesting topic. Was it prompted by Mira Grant's Parasite coming out next month?

That's about a genetically modified tapeworm that boosts the immune system... until things go wrong.

Or, in real life, would you include the strangler fig?

Birds drop the seeds (in the usual manner) on another tree and the fig grows around it, using it as support until the tree is strangled and the fig is strong enough to support itself.


If you want a plant? Dodder. It is like something right out of science fiction. It's like the Red Weed from "The War of the Worlds" ... except it is a pale green.

There is a wonderful timelapse video of it in David Attenborough's "Private Life of Plants", strangling the heck out of some nettles. My google-fu is week, so here's a video of it attacking some tomato plants:


I don't have a favorite parasite, but since I just came across it, I'll say the Vampire Finch. I was going to suggest the Cuckoo, or certain types of Orchids.


Not entirely -- there are a lot of genre parasitology novels out there, from Scott Westerfield's "Parasite Positive" through Seanan's "Parasite" (which I can recommend) to some of my own -- "The Apocalypse Codex" and "Equoid" to name two. But I guess I'm just in a parasitic frame of mind. Looking for something new to brandish at people until they cringe ...


Necator Americanus is my favourite parasite. I love them so much that I'm hosting around 75 of them in my intestinal tract at the moment. It's for a purpose of course, I'm not crazy. They calm my immune system.

I have multiple sclerosis, an autoimmune disorder that scrambles the myelin sheath of neurons in the central nervous system. Four times in my life I've had a "relapse", episodes where the cells of my immune system invade the normally peaceful domain of my brain and spinal cord. Each time has been a slightly different horrifying experience, as you'd expect from a cellular shotgun blast to your neurological tissue. Being unable to walk or swallow, dragging myself around the house. That is until the brain re-routes the fried functionality to new areas in the brain, a feature called neuroplasticity that most people never experience with such awareness, appreciation and dread.

Unfortunately, the areas damaged by the rogue immune cells become scarred. Your brain loses it's ability to re-route lost functionality. The limp becomes permanent. You drool sometimes. Many people wind up in a wheelchair.

Thankfully I'm not at that advanced stage of disease yet. Soon after my diagnosis (about 8 years ago), I read an article about helminthic therapy: using parasites for their modulating effect of the body's immune system. The hygiene hypothesis is the related theory, which, in a nutshell, posits that a modern parasite-free body is contributing to the rise in autoimmune disorders.

Long story short, I paid a lot of money and got a steady supply of gut worms. I haven't had a relapse since I first infected myself about 4 years ago. Of course, correlation does not imply causation. I can't say with certainty that they're a magic cure, but I also can't help but feel they've changed the course of my life.

So far, my only permanent damage is the inability to spread the toes on my right foot. Because of that, necator americanus is my favourite parasite.

(I should note, I'm incredibly grateful for the people who actually do the hard work of incubating and supplying the worms to me and others in need. The worms are great, but the people are saints. If there's an interesting story here, it lies with them and the troubles they've faced in their journey. Google Jasper Lawrence for more.)


Hmmm, I'd argue that symbiote is the more general first class, but whatever.

A couple of ideas: cats and dogs, AS WE CURRENTLY TREAT THEM. When you analyze our relationship in nutrient and energy terms, most of our pets are parasites. They take nutrients and energy from us, and provide none in return. This is one of the problems with the definition of parasite: how do you analyze it? Is the affection and companionship of a pet a vital commodity that makes its human's life better and possibly extends it? Or is it a social parasite that takes the place of a lover or child and immobilizes the human socially and/or reproductively? The answer varies depending on how you analyze our relationships with our pets, and it's neither simple nor uniform.

Now, about those non-human parasitisms. Are they any simpler than our relationships with our pets? Ummm, no. Or possibly yes. Mostly, we don't know.

Anyway, my favorite plant parasites are the orchids as a group. They start off as tiny little 18-celled seeds. These seeds can float in the wind like fern spores because they're so light, but they cannot germinate unless they are attacked by the right species of fungus (some orchids require a single species of fungus, some are more generalized). If the fungus attacks the orchid seed and it survives, the orchid starts sucking all the nutrients it needs out of the fungus and proceeds to grow, harboring the fungus in a specialized organ called the mycorrhizome. Once the orchid matures, it may green up, produce its own carbon, and dump the fungus, either temporarily or permanently. At least eight separate orchid clades never green up, retaining their infantile attachment to the fungus throughout their lives. Since some of the fungi some orchids parasitize are serious plant pathogens, in human terms, this is like a human infant growing to adulthood by sucking blood out of a tiger's tail, after the tiger invaded the nursery to eat the infant.

But orchid parasitism doesn't stop there. Orchids are notorious for parasitizing pollination relationships, tricking insects into pollinating them without any reward While this is not universal (some orchids are fair partners with their pollinators) it is widespread in the orchid family. The reason it works is because of those tiny seeds. One successful fertilization produces thousands of seeds, so orchids, more than most plants, benefit from tricking pollinators. The trick only has to work twice (once for each flower).

This is also why there are so many orchid species: all it takes is the pollen of one species getting onto the stigma of another, and they can potentially produce thousands of hybrid offspring with wildly different flowers that attract different pollinators.

But that's not all. Orchids have recently begun tricking humans into cultivating them on a huge scale. While some humans make money selling orchids, rather more hobbyists spend thousands of dollars on greenhouses, cultivation facilities (for those orchid seeds that can be grown on agar without a fungus), and so forth. One could easily argue that an obsession with orchids is a form of social parasitism--by the orchid. They've hacked our nerds, our geeks, our love of beauty, and our need for social status quite nicely, don't you think?

However, all this trickery comes at a price. Tricks only work when they're rare, and this is the main reason why orchids are so rare. After all, anything that has to cheat a fungus and a pollinator just to reproduce can only survive in a fairly small area where it has all the victims it needs.

Aren't orchids pretty?


If you want something from the inorganic domain, how about whiskering? It isn't technically parasitism, but it sure looks like it, and does have a lot of the characterstics.


...although see Bruce Sterling's short story "Spider Rose" for an interesting counterexample, although you could argue that it's about symbiosis rather than parasitism.


Okay, I think you just won.


You wanted plants Monotropa uniflora "corpse plant" is a 2 for. Feeds of fungi feeding off trees and they are pretty. My personal favorite is Armillaria solidipes Honey mushroom largest living thing we've got going on this marble.


Least favorite: Guinea worms. But at least they are on the way out, on track to be the first human parasite species ever to be eradicated by humankind. From the Carter Center website: 1986, there were an estimated 3.5 million cases of the disease in 21 countries in Africa and Asia. In 2012, there were 542 cases in four Africa countries, which was a 49 percent decrease from 2011.

God damn, that's progress for you.


Some days, I think I'm my favorite parasite.

I look at what I could achieve all by myself "in a state of nature", and then I look at the lifestyle I have, and I am struck by the mismatch.

(Other days, I of course remember that it's really because human society is not a zero-sum game, and cooperation improves things for everyone. But some days I don't always remember that right away.)


"Okay, I think you just won."

Thanks, but there's actually more interesting insights just below the surface of this story.

Necator Americanus is a parasite. That's a human definition, a label given to them in a time when doctors and scientists had a more limited understanding of their relationship with us. Their view was that these little worms drained our blood and used it to make eggs, end of story, one way relationship.

However, in light of their therapeutic effect, their biological relationship to humans can be seen as closer to symbiotic. Some of us actually benefit from their presence, or at least suffer from their absence.

But this probably wasn't always so. When the first necator americanus infected a human it was probably purely parasitic, looking for a host to literally drain it's lifeblood. But over thousands of years, the two species were in persistent contact. They were a constant part of each other's environment. It's only been in the last one hundred years or so that humans have existed en masse without intestinal parasites.

In other words, these little worms are a necessary little program for some of us, because we evolved with them. They are old friends.

(Most of this is 'original research', and probably has some logical stretches in it. I've thought a lot about it since I received the therapy, but haven't shared much with others. And some parasites are truly horrible, yet some parasites are, for some of us, necessary. It's a balancing act, like many things.)


I don't know if the Ophiocordyceps unilateralis fungus is my favorite parasite, more like the one by which I'm most morbidly fascinated.

If you're not familiar with this particular invader, briefly, it infects carpenter ants that live in rainforest trees and turns them into zombies, for want of a better word. Once the spore completely infiltrates its host, it forces the ant to travel to the underside of a leaf, where the host will bite down on a vein, anchoring itself for the fungus' fruiting body to eventually erupt from the ant's head. There, it will produce spores that will rain down on other unsuspecting victims.

Apparently, this particular fungus will infect cockroaches, butterflies, and other insects, but it has achieved the most successful manipulation of the ant.

If you want to read a more thorough description thatn my admittedly amateurish rundown, google something like "parasite fungus hijacks ant", and be prepared to squirm.

Also, do read Carl Zimmer's Parasite Rex, I can't recommend it highly enough.


Ah shoot, just realized that Ophiocordyceps unilateralis was mentioned in the original article. With a link, even!

Well. I'm still fascinated by them.


Gut bacteria are much closer to a symbiote than to a parasite, IMHO. There's interesting work being done in the field of "fecal transplant" (exactly what it sounds like) to (help) cure / treat a variety of GI-related conditions.

I was wondering if someone would mention the hygiene hypothesis, I was glad to read steven455's account. Some people are claiming that kids that are infected by hookworms grow up to have stronger immune systems / fewer incidence of auto-immune diseases.


Liver fluke - their life cycle is fascinating, and I'm told they produce some interesting immunosuppressants.


Scott Westerfield's book is Peeps. Stephanie Meyer's book is Host. The Attack of the Pod People from a pod person's point of view. Beats hell out of her sparkly vampire books.

Hey, Stross, why not a separate thread on parasite occupations?

There are some very specialized occupational professions out there, commensal, symbiotic, and parasitic. Extra points for one that's all three.


Naegleria brain-eating amoeba death results in 1 to 3 weeks


Um, digging around on the site I found a remark you made about Zynga many moons ago

Otherwise, the only links in the entry are to wikipedia entries about various parasites. Did I miss something?


If by "favorite" you mean "creeps you out the most" I'd go with parasitic cancer. Tumors that are themselves contagious? Brrrr. Luckily they're rare, with only three types known.

The first is Devil Facial Tumor Disease. It's transmissible by biting, which Tasmanian devils do a lot to each other. As the name says the resulting tumors appear on on the face. They eventually kill the devil as they distort the jaw and mouth so much it's impossible for the host to eat. The tumors are very aggressive, to the point where they threaten to wipe out Tasmanian devils.

The second is canine transmissible venereal tumor. The name pretty much sums it up. Dogs have sex, and the tumor grafts itself onto a new set of dog genitals. Fortunately these tumors aren't necessarily malignant.

The third is contagious reticulum cell sarcoma in Syrian hamsters. This one is transmissible by mosquito. Ugh.


Ha! When I mentioned Orchids I didn't bother with a link since I didn't think the wikipedia entry was too useful for this discussion. Your description is much better. I had only a vague notion of them as parasites; leeching off fungi, and living in available nooks in trees.


[i]Saccharomyces cerevisiae[/i], aka brewers yeast, aka baker's yeast.

We might not have civilization or even agriculture if this little guy didn't munch on our food stores and give us what is effectively an external pre-digestion system, and worse, we couldn't get drunk.


My favorite symbiotic relationship, that of the algae and fungi which form the lichen.

My favorite purely parasitic relationship is that of the "whiskey fungus" Baudoinia compniacensis upon pretty much any surface around distilleries: it lives off of airborne ethanol.

To bring everything full circle again, there's also quite a history of making alcohol from the fermentable sugars in lichen (though only when the cost of beet or cane sugar was too high).


"Christmas Tree" - it's a type of mistletoe which produces lovely golden yellow flowers anywhere from mid-October through to the end of February here in south-west Western Australia. Looks gorgeous as you're driving along the road at that time of the year, seeing huge clumps of them all the way along the verge.


Talking of Brewer's Yeast, I just saw this - could be a cheap way to stay drunk and become a social parasite:


The Babel fish.

Oh it has to be something that actually exists?

Rhizobia because I like living in a world where low input, sustainable crop growth is possible.


As with mitochondria, chloroplasts (the things in plant cells that do photosynthesis, the basis of [almost] all life) are parasitic cyanobacteria that turned symbiotes a long long time ago. Yes, those are the same bacteria that once came close to wiping out life entirely.


Since Charlie included symbionts in his original post, there's Hal Clement's Needle, featuring a symbiotic alien which protects its host from injury.

Also symbionts rather than parasites, but I rather like figs and fig wasps, which are so closely connected that they've been co-evolving for something like 80 million years.

I also approve of nitrogen-fixing bacteria that live in the root nodules of legumes.


bellinghman @ 1 Cats are COMMENSALS A category Charlie left out. Though they too, can be chilling ... "The Commensals of Orgoreyn" in "The Left Hand of Darkness" for instance. I would suggest that symbiotes may never have been parasites, since in a symbiosis, both sides benefit. Think LICHENS ....

Oh, Charlie mentioned plants ... Dodder - genus Cuscata will do for a start!

Are Fungi; which are emphatically NOT plants, parasites?


Charlie @ 23 Also, human habitation attracts birds ... As I found out on Monday, coming back from t'plot ... "Why can't I get the front door open properly?" Asnwer: Because unspeakably cute tom-kitten has planted a dead Wood-Pigeon behind it .....


The Loa loa worm - see also interviews with Sir David Attenborough as to why he refuses to have anything to do with "creation" ... a worm that burrows into people's eyes, euuggghhh .....

Talking of fungi, as I was, the season has started ... Several yellow Russulas, a yellow-cracked bolete & 2 or 3 Bay bolets ... going to make cream of wild mushroom soup, OINK


You mentioned two parasites in your comment. Zynga was one. The other was the ant fungus, which Charlie had already mentioned in his article.


You want plants? Broomrape is awesome. Beautiful and really hard to get rid of. And has a horrible horrible name.


I like some of the TSEs. Kuru and scrapie for example. BSE lets me sneak in a politician reference with Selwyn-Gummer Pater and Fila and that publicity photo. Of course it's arguable if they're really parasites but a lot of these definitions are a bit blurry these days.

So if I have to go for one where there's no, or little, doubt, I'm going to go for Echinococcus granulosus for a very simple, human reason. My first proper, adult relationship, we fell in love over her finishing her research project into E. granulosus. I learnt more about hydatid disease than I probably wanted to but got a lot more out of it than that.


Awww! I now have this sweet image in mind of the two of you snuggling together and taking turns to look down a microscope.


Are Fungi; which are emphatically NOT plants, parasites?

As a group? No. There are plenty of non-parasitic fungi.

As individuals, many (perhaps most, but I barely qualify as a layman on the subject) are. Fungi are the group mostly responsible for breaking down dead matter, and some do anticipate that a bit. Seeing a fungus growing on a still-live tree is sad for me.


I think you'll find Scott's book got a different title for the UK market.


Parasitic mosquito-transmissible cancer that affects humans would be one hell of a medical disaster novel plot, wouldn't it? (Now, I wonder what kind of cancer would be creepiest. Mind you, just the idea of an insect-transmissible cancer pandemic with everyone lurching around on chemotherapy drugs the whole time is pretty creepy ....)


I think mosquito-transmissible HIV is more likely.

On a positive side, the solution will involve eradication of mosquitoes.

Well, positive for humans, not for the food chain...


Worked out quite well for them. They found a big species that didn't want to eat them that liked to pile up the same food that their prey ate. And on top of attracting prey, these big animals created nice dry artificial caves all over the place. They even had handy paws, and enjoyed touching cat fur and removing any skin parasites.

The best part is that these big dumb animals even started doing a lot of the hunting for cats, and threw away the best parts of the animals for cats to eat. Many cats could relax and just hunt recreationally.

The only down side is that dogs got in on the racket too.


There was an FPLC and an ELISA reader too... but that's not far from the truth. There may have been lunches, and some moments away from the lab as well.


Once you explain (with pictures) necrotising fasciitis it's nastier than cancer.

In an appearance obsessed society, malignant melanomas are a pretty creepy form of cancer. Particularly if you want to play nasty games with racial tension too.

Anything that targets any of the pituitary hormone producing tissues could be 'interesting' for some quite creepy values of interesting. They quite often produce big changes in behaviour which often disturbs people a lot.


Well, there was that jolly little story by Kornbluth, "Friend to Man." Somewhat sympathetic to the parasite's viewpoint.


For short stories there's "Bloodchild" by Octavia Butler. It happens to be online courtesy of the Washington Post. The story "The Things" by Peter Watts may also qualify, as it's The Thing from the Thing's viewpoint. It also happens to be online.


Parasitic mosquito-transmissible cancer that affects humans would be one hell of a medical disaster novel plot

I was going to say that reminded me of Tasmanian Devil facial tumor disease, but found heckblazer @50 already got there. His comment wasn't there last night when I posted what is now @51. Poor Devils, they're almost cute normally.


Then I go and realize that's what you were responding to. D'oh!


Yeah, sorry. Some comments get hung up in the automatic filters, and it can be a while before a mod notices it and lets it through. If it's been too long, then we may leave it there rather than have it pop up way after anyone following the conversation is likely to see it.


That's what I assumed. Devil tumors popped into my head and I got distracted by looking it up and didn't notice what Charlie was replying to, but did a quick search through the comments.


"Diplomatic Act" by Peter Jurasic has a whole bunch of different alien species, and one of them is parasitic (not symbiotic -- kills its host), and is portrayed fairly sympathetically. However it has a very minor role in the book, not a "viewpoint".

Note that while Niven's Puppeteers are herbivores, they are also parasitoids -- their larva feeds in the body of another species. However Puppeteers consider themselves symbiotic with that species, and refer to them as "females".


There is this short story by John Wyndham, where some attackers from "Ghanistan" attack Britain by tricking garden freaks to plant giant fungi in their gardens. These are modified such that they grow both on dead and living matter. I don't know the original title, just the Dutch version: "de plofbollen".

That's nearly as scary as his "red stuff", but that isn't a parasite, just a scary substance that overgrows everything.


I'd hazard the most likely cancer is one that's endemic to the circulatory system, since this is something that has to be easily sucked up by a mosquito. If my Google-fu is correct the Syrian hamster cancer is one that affects the lymph nodes, which makes sense as that's a logical place for cells injected in the bloodstream to end up.

As for the creepiest cancer, I'd go with malignant teratoma. A tumor with teeth is just wrong (warning: that link goes to a picture). As a speculating layman I suppose a stem cell treatment gone horribly, horribly wrong could do that. Stem cells might also explain the lack of initial immune response to the foreign cancer cells. In the case of the poor devils the guess is a lack of response is due to limited genetic diversity from a population bottleneck.


Note that while Niven's Puppeteers are herbivores, they are also parasitoids -- their larva feeds in the body of another species. However Puppeteers consider themselves symbiotic with that species, and refer to them as "females".

What is it with Niven and species with non-sentient females? The Kzin are also like this.


I guess that'd be his 1933 short story 'The Puff-Ball Menace' mentioned here.

(Not that I've read it, but I Googled™ what I guessed was the most likely translation of that Dutch word.)


Can we have Tok'ra? (Stargate)

Symbiotic, heals most things, makes us live longer and lends access to more knowledge - also gives you a strange voice... The downside is a time-share on your body.


I'm at #85, yet still first to say "memes"? O_o


The better way to think of fungi as a phylum is that they're organisms that grow in their food. There are a number of parasitic fungi (and epiparasitic fungi, for that matter), but there are as many (or more) non-parasitic fungi. I'm pretty certain that, by mass, most fungi are non-parasitic. It's unclear whether it's true by species, because we have little idea what most fungi do for a living.

The one most of you are familiar with is good old Saccharomyces cerevisiae, aka yeast.

To clarify for those (like Charlie) who are a bit unclear on the concept of parasite:

A relationship is parasitic if one partner benefits while the other is harmed

A relationship is mutualistic if both partners benefit from the relationship

Commensals live together, without either benefiting the other

Symbiotes live in close physical proximity (typically tissue to tissue). Many people assume that symbiotes are also mutualists, but that's not strictly part of the definition. The critical part of symbiosis is the close physical association, not which partner benefits.

For example, gut bacteria are symbiotes and (generally) mutualists, not parasites.

Despite what you haven't heard from your biology teachers, symbiosis is the norm for most organisms: most species depend on other species, such as the gut organisms that almost all animals have, the fungi that serve as part of the immune system on plants, and so forth.


organisms that grow in their food

That's possibly a little bit simplistic, but it's a lovely first approximation. Sure, I can think of both animal and plants that do it too, but most animals and most plants don't.

(And what that biology teacher may also have neglected to emphasise is that typical plants get the large majority of their substance from the air, with most of the remaining being water through their roots, and only traces of minerals. So plants do not grow usually in their 'food'.)


Agreed. It does get at the key point that fungi acquire their nutrition by secreting enzymes and other substances into the substrate they grow in, and taking in the resulting nutrients directly through their cell walls (and membranes). Incidentally, this thumbnail definition came in the first few minutes of my mycology class, and it was a mycologist who came up with it.

There are other organisms that have adopted a fungal lifecycle (oomycetes for example, which were brown algae at one point), but very few animals and plants have done so, and all of them (so far as I can think at the moment) are parasites.


Orchids and mistletoe have been mentioned, but there's a nuance here that I think has not been discussed: Epiphytes and lianas (vines) can be characterized as "structural parasites". They rely on their host to get them up above other plants (more light) and out of the wind boundary layer near the ground (better seed/pollen dispersal) and don't invest in nearly as much infrastructure themselves.

So let's hear it for grapes, a structural parasite.


The Kzin actually bred their females into nonsentience. Chmee encounters a talking female in Ringworld Engineers and the concept is fully explored in the Man-Kzin wars where an ancient Kzin preserve has fully sentient females.

Then of course is the story "The survivor" by D. Kingsbury where a kzin experiments on a human prisoner to render her appropriately non-verbal.



Since Charlie included symbionts in his original post, there's Hal Clement's Needle, featuring a symbiotic alien which protects its host from injury.

If we're going to include fiction, I'll throw in the nameless symbiont known as "the wind" in Brian M. Stableford's Grainger books. I wouldn't want to be a host for it, but it would have been fascinating to talk to...

Think of something like a goa'ould, except actively helpful.



"Diplomatic Act" by Peter Jurasic

clickety... good grief, it's Londo Mollari from Babylon 5!

Strac gave him some good lines:

"On my world, we have learned that an inauguration is simply a signal to assassins that a new target has been set up on the firing range."

Centauri politics were fun for the whole community...


I still remember the symbiont in Sturgeon's The Girl Had Guts


Larry Niven does non-sentient sexes in both ways. Grogs and Chirpsithara have stupid males. Actually he also has species which are non-sentient in parts of their lifecycles.


I nominate slaver ants. They even exploit labor of other species. Thus they take parasitism to a new high (or low depending on viewpoint)


Wolbachia ( ) ( mentioned earlier) is a really interesting organism. It is one of the most common and successful parasites out there. It works in effect by applying DRM to the gametes of the species it colonizes. In effect this produces a spontaneous speciation event. This or a similar mechanism would be an interesting origin for a biological conspiracy.( ala the hybrid deep ones -- if you make them only auto fertile/ fertile with parent species then there is a built in biological mechanism to punish those who leave the flock...)


Can't believe I'm the first one to mention it, but the bot fly (or botfly) is super-creepy and fascinating. The larvae (aka maggots...) burrow under the skin of a live mammal. They feed on the flesh (and prevents it from becoming infected somehow) until they're ready to come out, fall on the ground and change into another botfly. The adult botfly is large and makes a loud buzzing sound that is somewhat characteristic. Some animals have learned to run away when they hear that buzz. The botfly's solution is to capture another insect (a smaller fly or a mosquito), stick its eggs on it, and let this other insect take care of the last mile delivery.

There's a dedicated human bot fly. Just google the term and go straight to the pics.


Well, an Oncovirus might do the trick:

Come to think about it, who's to know there isn't already an oncovirus transmitted by some insect vector around we just haven't identified yet...


Hm, I always thought the plants the parasites in this relationship; enslaved the poor cyanobacteria and even stripped them of their ability to live independent lifes...


Well, IMHO it's more like humans evolved quite a few machanisms to deal with worms, and some of those are potential harmful if there is no target around, just like a IR AIM might target your own jet. Throwing some chaff, e.g. swallowing Necator eggs, might help if that's true.

As for "what doesn't kill you makes you stronger", I guess Nietzsche might have put some modifiers to that if somebody explained neurosyphilis to him. Or fronto-temporal dementia, to go for the other suspect in ca


And, even more insidious, P elements, other transposons

or selfish DNA in general:

Which one MIGHT have been viruses, or evolved into viruses in some cases, or are an independent evolution. Some are advantageous, some deleterious, with most, we have no idea what they do.

To continue the recently established tradition of male-bashing here (err, just joking), one could argue the male-inducing Y chromosome in mammals, and maybe the female-inducing W chromosome in birds and some reptiles, are on a path of becoming parasitic DNA. There is already quite some gene loss, and it seems possible that at some future point, the sex-determining parts go over to some autosomes, thus making the old one really obsolete.

No male-bashing, but it's a cold fact the whole sex thing in most metazoans is somewhat closer to parasitism than mutualism; this is especially so if you go with the sperm competition theory for anisogamy:

Though then, newer theories point to the cooperation and specialisation of different mating types; also note there are quite some examples of high male investment in the offspring, e.g. seahorses or that strange neotenous, somewhat bald member of the Homininae...


Try this for a creepy parasite: it sends cells wandering around your body into every organ, where they can settle down, blend in, and grow.

Every organ, including your brain.

Well, maybe not your brain; but probably your mother's:

After a baby is born, it may leave some fetal cells behind in its mother’s body, where they can travel to different organs and be absorbed into those tissues. “It’s pretty likely that any woman who has been pregnant is a chimera,” Dr. Randolph said.

As scientists begin to search for chimeras systematically — rather than waiting for them to turn up in puzzling medical tests — they’re finding them in a remarkably high fraction of people. In 2012, Canadian scientists performed autopsies on the brains of 59 women. They found neurons with Y chromosomes in 63 percent of them. The neurons likely developed from cells originating in their sons.

The full story is here:


BTW, to tread somewhat close to the precipice, hey, you get the best view there, while human job descriptions might be off-limit, what about other, err, cases of intraspecific parasitism. To be somewhat more specific, sociopaths are quite often labelled thus, with the nice added problem of culpability.

Which might generalize somewhat like this:

  • a non-sentient parasite without moral qualms, no problem
  • a sentient parasite with moral reasoning, in fault (a vegan might argue we're this to cows, though one could argue it's more like mutualism)
  • a sentient parasite without moral qualms, somewhat tricky...

Ringworm - a family of really successful fungal parasites which we will probably never wipe out, but aren't in themselves very dangerous.


Cool factoid about slaver ants: They have to put up with slave rebellions, or at least slave sabotage.


Well, sexual reproduction as a system is rife for parasitism; for starters, while we are used to think of 50:50 genetics, this is not really the case, see mitochondria. One explanation is those little parasites are quite jealous little buggers.

But than, who is to say one of the sexes doesn't slip in an extra allele or two; there is one theory genomic imprinting evolved to make such an idea quite costly:

As for the more traditional cuckolding, err, I sometimes wonder if the "go for a partner similar to yourself" component of human mating is not just some quirk or a mechanism against genetic incompatibilities, but more of a way to make sure

a) the children are somewhat similar to the non-biological father

b) the children the non-biological father nurtures have at least some of his genes

To come back to the fetal cells in the mothers' brains, since pregnancy is an economic conflict between pregnant female and embryo, with death of one or both sides not that frequent, but not that unknown either, influencing the host's behaviour seems an interesting strategy...


I'd usually say that sex (in the meiotic sense) is the eukaryotic response to death. Many simpler organisms reproduce both asexually and sexually. They clone themselves when times are good for them, then have sex when times are bad. The apparent answer is that they need to reshuffle allelic hands to meet the new threat. While this happens often with environmental cues, it's also a response to parasitism.

As for anisogamy, don't get too hung up on the tetrapod sexual landscape. Lots of animals (such as many reef fish) and most plants are bisexual, and that doesn't even get into the weirdness of fungi (between 0 and 289 breeding types). There are certainly different advantages to producing sperm vs. eggs, but it's more about reshuffling the deck, as much as one sex parasitizing the other.


Well, I guess one of the things we have established in this thread is parasitism and mutualism are quite close; as for the unequal investment of both sexes to reproduction, well, it's somewhat advantageous to the mother, too, half of her offspring are similar cheaters.

Funny thing with the hermaphrodites, at least in some cases there is some selection how much to invest into "male" or "female" reproduction. Or ways to determining who's butch and who's femme, e.g. fencing in some flatworms. Or sperm corrosive to tissues in others.

No need to speculate about the psychosexual problems of the biologists researching that one, we already did it. One of the suspects summarizing his research with asking "what are men good for?" was not exactly the best way stopping the resident clique in the last line[1] joking about inferiority complexes.

[1] You know who you are. Wanna continue our RPG sessions?


Cochliomyia hominivorax aka New-world Screwworm Fly too.


Tinea cruris - makes me want to scratch just thinking about it.


Felling Consider Wolbachia. This parasitic bacteria lives in the cytoplasm of various species of insect and kills all the male zygotes. The bacteria is transmitted by females in egg cytoplasm. Why let the host make males that don't produce eggs with Wolbachia infested cytoplasm? But, when the female wasp eats an antibiotic, the males of the species appears. Some fungi infested insect nectar or equivalent source of antibiotic. I'm thinking that the insect is quite happy producing twice as many females and therefor twice as many grandeggs. But female only species can't exchange genes and tend to die out. The ability to make males every once in a while could be usefull. Is Wolbachia a parasite or a symbiote?


Dodder (Cuscuta and Grammica; see

In the animal kingdom, Ommatokoita elongata, which infests the eyes of Greenland sharks.


Fictionally, I liked the sentient morels that hitchhike as extra cerebral cortex on [d?]evolved humans in Brian Aldiss' Hothouse, aka The Long Afternoon of Earth. Maybe dubious as biology, but great imagery.

On second thought, not dubious biology. As a descendant of the Burgess Shale gang, I have no business betting against evolution doing anything over a billion years.


Well, the morels are fruiting structures designed to loft spores or get eaten, so they're not good computing models.

That said, rowdier mycologists do wonder how well the bodies of fungi (the mycelium growing in its substrate) process information. As with plants, fungi don't move, but their growth patterns has many similarities to the foraging behavior of animals, and they have the ability to sense and respond to a wide range of chemicals through growth and chemistry. They may not think in a mammalian sense, but it's quite likely that there is an emergent intelligence similar to that of an ant colony as signals interact (and possibly quorums are sensed) across the body of a mycelium. It's likely that something similar happens in plants too.


Now you're getting at the central problem of the language of symbiosis. To start towards a partial solution, answer the following question, without thinking: "Would you categorize red as white or black?"

The point here is not that there is an answer. Red is neither white, nor is it black, nor is it gray. The best answer is, "this question is BS." I'm using it to demonstrate the trap of dichotomous thinking, as symbolized by "X is either A or B." When we have terms like parasite and symbiont, we naturally try to shoehorn phenomena into them, on the assumption that these categories are mutually exclusive or at least distinct. When you're dealing with a symbiosis, the categories are artificial, and you can (like the majority of researchers, at least part of the time) massively delude yourself by getting caught up in dealing with the categories rather than the realities.

Upstream in #86, I did bring up the standard definitions of symbiont, parasite, mutualist, and commensal, mostly because of trap #2, which Charlie fell into in writing this post.

Once people realize that the categories of symbiosis are artificial, those who don't walk away in disgust generally start getting careless about how they use the words. They assume that they can use any word they want to mean anything they want, because the categories are so mushy. Because they're not thinking clearly, the result is generally Babel. If you're lucky, it's miscommunication or argument.

In symbiosis research, this is a huge problem, along with the muddle-headed thinking that generally results from it. For example, if you ask a bunch of biologists what the words "symbiosis" and "mutualism" mean, and how they differ from each other, you will get multiple answers. If you're lucky enough to do this at a meeting, you may also get a vicious argument, because the biologists generally assume they are right and automatically defend their positions against the idiots around them.

How do you deal? Think like Einstein, or (better yet) Dr. Ruth. Symbioses are complex relationships, but humans are used to complex relationships, at least with other humans. When you're talking about a symbiotic relationship (symbiosis here meaning two organisms living in close association), you've got to provide a relationship frame. You can frame their interactions in terms of energy flow, nutrient flow, information flow, reproductive outcomes, over different periods of time, and so forth.

You will find that, depending on the frame of reference, relationships vary. An organism like the family dog may be a parasite for years (in terms of taking food from you without providing you any food), but it may save your life one day. Wolbachia may be a reproductive parasite if you are a male insect, but it may be part of a complex symbiosis from the point of view of the plants that are affected by Wolbachia-infected insects. As romance novelists have known for centuries, understanding settings and time frames is essential in describing relationships and how they change.


A contagious cancer epidemic seems even less plausible than most thriller plots, though. Cancer's dangerous because it's part of you - your immune system has trouble targeting it, and so do medicines. Someone else's cancer will be readily targeted by your immune system. Viruses that increase your chances of cancer are common - but one virus that straight-up gives you cancer seems less likely. Multiple redundant cancer-suppressing DNA sequences and all that.


You have met the Human Papilloma Viruses haven't you? HPV 16 and 18 are recognised as the major causes of cervical cancer. Yes, there are other steps in the chain as well, but you've got at least one fairly short causal chain viral infection => cancer.

It's certainly close enough for a bio-terrorist thriller plot without distorting the science to the point of having everyone that knows their bioscience screaming. There could be faint blubbering around the edges for a range of other mistakes of course but there's at least one model you could base it on.


While I agree that contagious cancers are a good plot item (as the Tasmanian Devil facial tumour disease shows), it's not a good terror weapon, because cancers spread a bit too slowly.

One could rather write a plot akin to the plot of Twelve Monkeys, where someone decides to, oh, bring the human population down to sustainable levels, and lets loose a cancer virus without telling anyone or taking credit. Years later, a plague of cancer overwhelms oncology clinics worldwide, and people are racing both for a cure, and then (as with StuxNet) to keep the virus from being coopted by others, to be used for their own agendas. As with HPV, it could even be a sexually transmitted disease.


Another idea might be an epidemiological crime story, e.g. there is a higher cancer rate in some population, e.g. near a nuclear power station. First tests show this to be no statistical fluke, and the most popular cause is ruled out. After some distractions, we get to the reral cause, a vector-bourne disease. Which, alas, was caused by some environmental impact of said power station or whatever. With a solution opposed by some professional donation grab, err, environmental organisation in the vain of Greenpeace or PETA.

Going for some low shots at Greenpeace et al., industrial lobbyist etc. might add some flavour.

Anybody feel free to use this.


I agree, sorting everythin into symbiosis and parasitism is as futile as sorting red into black or shite. Though in the latter case, if you go with the HSL system, it might depend on the red in question:

Thing is, going for intricate, complicated relationships might not be what you want in a horror story. In the same vain as "psycho sexual partner from hell" aims for a different clientele as Jane Austen...


Would you believe a parasitic blueberry? Pterospora andromedea goes by the street name of "Pinedrops" and gets it carbon courtesy of a fungus.


Aren't they cute? Wikipedia has an entry on this phenomenon under mycoheterotrophy. Neat thing is that, so far as is known, most obligate mycoheterotrophs (like the pine drops above) specialize in parasitizing only one (or at most a few closely related) species of fungi.


Yes, that's exactly the main example I had in mind. (There are plenty of others.)

HPV is extremely common. But the great majority of HPV-infected people do not develop cervical or other HPV - associated cancer.


Bellinghman @ 66 Err – what about “Beefsteak Fungus" – delicious if cooked properly?


Vanzetti @ 82 I would guess it’s really heavy irony, directed against those groups who regard women as inferior, for whatever “reason” ….. Like Niven’s perpetual “green” thread, which is preachier, though.

A couple of ideas: cats and dogs, AS WE CURRENTLY TREAT THEM. When you analyze our relationship in nutrient and energy terms, most of our pets are parasites.

Also, emergency food supply.


Don't all animals eat plants or plant eaters? Aren't plants alive?


Plants are alive, but there are many animals (grouped as detritovores) which eat things like fungi and bacteria, as well as the wastes of other organisms. Things like worms and fungus flies come to mind. It's easy to forget, mostly because the conventional models of food chains don't capture the decomposition phase of nutrient cycles very well.


How about the rat lungworm, Angiostrongylus cantonensis?

It's yet another parasitical nematode from the tropics, with a typical lifecycle veering between many varieties of snails and slugs (in its larval form) and rats, where it first takes up residence in the brain, then grows to its adult form in the pulmonary arteries. So far, so good.

However, if humans eat infected snails or slugs - either intentionally, or unintentionally in the form of a tiny slug clinging to a leaf of produce - things abruptly get particularly nasty. Following their natural course, they enter the bloodstream, and arrive at the brain. However, as we are not rats, to the infecting larvae nothing seems quite right. So they'll burrow in, and burrow a little deeper, and deeper, and deeper...

Says Wikipedia, with uncharacteristic understatement, "The presence of parasitic worms burrowed in the neural tissue of the human CNS will cause obvious complications. All of the following will result in damage to the CNS: 1. Direct mechanical damage to neural tissue from the worms' motion; 2. Toxic by-products such as nitrogenous waste; 3. Antigens released by dead and living parasites."

Symptoms of "Eosinophilic Meningitis" as the result is labeled resemble meningitis, starting with agonizing headaches and possibly ascending to paralysis, coma, and death. The outcome all depends on how lucky you are; at this point treatment is largely symptomatic because they haven't yet learned what is effective against the larvae. "Removing Cerebrospinal fluid at regular 3 to 7-day intervals is the only proven method of significantly reducing intracranial pressure and can be used for symptomatic treatment of headaches. This process may be repeated until improvement is shown. Recent studies have shown that treatment with an antihelminthic such as mebendazole or albendazole combined with prednisone or prednisolone can reduce the severity and duration of headaches but have not been shown to improve long term neurologic outcomes."

Thanks to global trade, these charming little fellows are spreading throughout the world. A man on the Big Island of Hawaii died of it a year or two ago; the cause was eventually traced to unwashed lettuce he had eaten in a salad, which must have contained an infected slug larva.


How about give the cancer some of the characteristics of leprosy with constriction of peripheral blood vessels which induces gangrene and necrosis, you're left with shambling rotters. They're not zombies, far worse off than that -- they're still alive and aware as well as phenomenally contagious.


I like the cancer dog parasite, mentioned previously.

This parasite is the cancerous form of dog. It is a dog. Arguably the best dog as it has spread world wide and lived hundreds, maybe thousands of years.

Get a dog with this cancer and you have two dogs! Once nice furry one, and another tumorous parasite dog living inside your furry dog.

Parasitic ants are really neat. They live within the colonies of other ants. Some of them kill the queen and just take over, but clamp onto the queen and slowly kill it while laying eggs of their own.


The correct answer is "The Corporation" right?

It's a great place to start. Now I believe OGH's proscription was on describing humans as parasites, not on parasites of humans. With that assumption in mind...

I know there's flak back and forth over memes. Sticking with the basic definition: "an idea, behavior, or style that spreads from person to person within a culture." On the benign end we get Gangham style, on the horrific end we get child sacrifice.

I remember being horrified in Sunday School reading about the Israelites and how they would be seduced into the religious practices of their neighbors, including sacrificing children to Moloch. Now I know there's controversy about whether this was just old Hebrew propaganda but, as someone still a child myself, I found it horrifying to imagine that there might be something persuasive that could convince good parents not unlike my own that the best course of action was tossing their children into fire.

Now even if the Moloch business was complete bunk, you've got many child sacrifice cultures with Meso-Americans. You may have a mitigating circumstance where the people involved might not really see it as death in the same sense we do, that they weren't really extinguishing a human life. But they were.

There's something powerful in these belief systems. Everything from National Socialism to Scientology to Corporate Capitalism. The ideas seep into your brain. At the lower levels, it makes you a willing and compliant victim. As someone higher up the totem pole, you gain strength and power from the structure. You have a vested interest in perpetuating and extending it. And there are all sorts of mental tricks to employ to convince yourself that the evil you're doing isn't really evil, or that it could be justified as necessary.

If we look at corporatism as a parasite culture, we can see how tribal and familial ties and obligations are destroyed and and the people are assimilated into the collective, as workers and consumers. And money sits there at the center of the web, wealth compounding through no effort of its own, driving humans to desperate acts of cruelty not unlike throwing children into the fire, manipulating our brains with greed and fear. The world we're living in is like Lovecraft by way of Kafka. And the worst thing about all of this is that we don't even have a "thing" to blame. Cthulhu isn't behind the corporation, there's no real "it" there. Hey, high priest! It's not Quetzalcoatl ripping out hearts with an obsidian blade, it's all you. Hey, CEO! It's not the free market telling you to lay off all your workers, it's you.


About the mod policy, some posts get held and some do not. My last post is held. No links or anything in it. Is the triggering factor length?


Mmm, yea malfunctioning parasites too. Swimmer's itch.'s_itch

Little worms, that are looking for a duck, find a human and burrow in. Then die because you are not a duck.

And now you have a dead tiny worm in your skin and so an itchy bump (or few dozen bumps) while your body clears it (or them) out (usually successfully).


Length is often to blame, yes, and that's quite possibly the case here, though length alone is rarely the problem that trips the filters — it's usually the length that results from repeated usage of certain (various) terms. Quite which terms is another matter.

However, given that Charlie has got quite tired recently of continual arguments about religion and that he has already disqualified discussion of classes of humans from this thread, I'm inclined to leave your comment unapproved.

Once he gets back from London and has recovered from a wedding that had more Hugo winners attending than many conventions, service may be back to normal.


Hmm. I wasn't going with the politicians and lawyers as parasites angle, humans as parasites, more along the lines of memes and social structures turning humans to victims. Humans as parasitic host seemed to be within the bounds of discussion here, or so I thought.


The automatic moderation is triggered by some magic regular expressions matching common spam subjects/phrasing. There's also a distributed blacklist service, which is accurate but a bit opaque (it's possible you may be blacklisted because an IP address you've currently got was previously assigned to somebody relaying spam -- possibly inadvertently).

Situation not aided by all the UK moderators being at the same wedding over the weekend.


Good to know, thanks. Hope it's a good time!


Further thoughts on unsuccessful parasites such as the rat lungworm:

One standard scientific trope in SF (where it's not simply ignored) is to assume that genuinely alien bacteria, parasites, and similar life forms would not pose a threat to us; because our biochemistry would be too different, they wouldn't be able to successfully infect or "digest" us. But what if the outcome of that unsuccessful infection was worse than a successful infection?

I'm no microbiologist, as will be obvious, but as I understand it in infections with some common bacteria, the damage done by the infection itself is miniscule in comparison to the damage done by the immune system's massive over-reaction to the chemical signals from the bacteria, causing septic shock. Imagine how the immune system might react to some truly alien chemical signal? ("My blood is turning to vanadium! I am becoming a sea squirt! Must do something now!")

For alien parasites... I actually have trouble thinking of something much worse than the lungworm case, except maybe hungry parasites which stay hungry because they can't digest what they're eating, which is quite bad enough. I'm happy to let my imagination be mercifully limited, as HPL said, and will let others think of still worse possibilities.

To cross-fuse this with gmuir's comment, some human memetic systems seem horrible or alien enough - what would a genuinely alien meme be like? And what might some sapient alien's equivalent of a cat macro or funny YouTube video do to us, if we couldn't take it in due to too-great differences in conceptual structure? I guess Alan Moore already tried something along those lines, with the Aklo in his Neonomicon series, but I'm sure there is room for more exploration.


As far as alien memes, the Parrot is creepy enough to give me chills.

The Langford Basilisk is a favorite. OGH has made a few sly references to it.

"BLIT (which stands for Berryman Logical Image Technique) is a short science-fiction story written by author David Langford. It features a setting where highly dangerous types of images called "basilisks" have been discovered; these images contain patterns within them that exploit flaws in the structure of the human mind to produce a lethal reaction, effectively "crashing" the mind like a poorly-programmed computer."

The idea of an image that can kill is just straight out freaky. Something similar was used with Peter Watts' vampires, something about right angles causing their brains to seize so they need special medication to remain functional in the modern world.

But more specifically about aliens, I read a short story years ago where geneticists were working deep in DNA research and discovered signs that humans were engineered at some point. But as a fail-safe from the designers, humans actually looking at the raw genetic code (via a computer monitor in this case) caused death. I can't find the name of the story. Aliens using a mind-killing fail-safe in Macroscope, though I've never read it.

I've always seen Lovecraftian madness and the tomes associated with it as a kind of mentally radioactive. Rather than turning the victim into a radiation mutant like in bad scifi, the ideas take up life in the victim's mind, prying the third eye open so it can be blasted with some eldritch pepper spray.

Memetic prions in the brain, Ice-9 in the membrane.


I'd probably go with corn as my favorite parasite for today, because it tastes rather nice (and I'll claim it's a parasite because it destroys the soil it grows in - sugar cane is harsher, of course, but personally I've never enjoyed cane all that often).

That said, I find other "parasites" more fascinating, but I run into naming problems. For example, the communicating collections of dental bacteria - do they even have a name?


My favorite Lovecraftian meme is that Azathoth is the central black hole in our galaxy, Yog-Sothoth is the galactic equivalent of the interstellar internet, and Nyarlathotep is the equivalent of Siri, which is why humans don't generally interact well with it, whilst more advanced aliens form cults to worship it. In this version, some of the Great Old Ones may well be apps, while the Necronomicon and other dread grimoires are Medieval and pre-modern hackers' attempts to reverse engineer user's manuals from their interactions with these unspeakable systems, which is exactly as crazy as it sounds.

This might (or might not) combine with other notions about the Lovecraftian universe, such as my feeble and Lovecraftian attempt to explain the Fermi Paradox.

Hopefully this is a sufficiently parasitic meme to pass muster.


"Imagine how the immune system might react to some truly alien chemical signal?" Well, if they're too alien to use proteins, the immune system might not react to it at all. Most allergens and antigens are proteins. Retroviruses slip by the immune system by having no protein coat....

So if alien germs could digest us at all we'd be in big trouble. Alien allergies seem a little less likely to me.


There is actually something similar around to Peter's antieuclidia addicted vampires for a certain percentage of the population, e.g. those with photosensitive epilepsy:

or, more general

Come to think about this, most of the triggers mentioned are somewhat unpleasant to me, e.g. leading to headaches, too, especially with sleep deprivation, and AFAIK I have no epilepsy, but then, I guess I'm on one or two spectra[1] that are somewhat associated with problems with sensory integration and, well, seizures, so I don't know how much one can generalize this being somewhat universal to HSS or just a sign of my personal ideosyncrasies...

[1] Migraine has quite some features in common with epilepsy; and the relationships between ADHD, autism and epilepsy are quite complex.


Well, my personal favourite parasitic meme is still Roko's Basilisk. Or "The Game":


Oops, I meant viroids, not retroviruses.


what if the outcome of that unsuccessful infection was worse than a successful infection?

"Bios" by Robert Charles Wilson. Go read. (It has some other fun biological first-contact speculation -- including one that permanently pencils in H. Sapiens as incompatible with the rest of the galaxy. And it's really a meditation on alienation and loneliness. But IIRC the core idea of the story is a planetary biosphere so hostile that exposure to it results in death through anaphylactic shock within minutes, evolving through epigenetic modulation that gives it some semblance of a Lamarckian process, and a human expedition marooned in orbit around it. Caveat: I read it some years ago so the memories may be garbled.)


For alien parasites... I actually have trouble thinking of something much worse than the lungworm case, except maybe hungry parasites which stay hungry because they can't digest what they're eating

This is a bit contrived. But: we know about Toxoplasma Gondii's happy-fun behaviour reprogramming in mice (and, possibly-although-it's-controversial, humans). How about one from an exotic source (probably synthetic biology gone feral) that requires a few mercury atoms to make the active centres of some of its enzymes settle into the right conformation? It's not designed to infect humans, but if it does -- by accident -- it makes the unwitting host go in search of mercury contamination to marinate in. Preferably organomercury compounds. Minamata Disease FTW ...


I second that. Really anything by Robert Charles Wilson (not to be confused with Robert Anton Wilson) is a good read. Going back to the earlier time travel threads, he may have written one of the best time travel novels that doesn't have anyone or really anything travelling in time...


Albino Redwood (Sequoia sempervirens). Grows as a parasite on its parent tree.


I'm really suprised no-one has mentioned the must-read book on this subject: Parasite Rex by Carl Zimmer ... I believe there is a free-to-download .pdf available as well, so if you google for it ...


Hepatitis D, it's actually a parasite of the Hepatitis B virus, since it has no protein envelope, and it needs to use those produced by Hep B. A virus that parasites another virus, that's mindblowing to me.


Well, apart from the mentions at comments #24 and #43?


Re: Disease memes crashing the human brain, "Snowcrash" obviously. And there-in the Tower of Babel myth as a metaphor for the parasitic memes that are human languages taking over and manipulating human minds.

Re dangerous images, I wonder about QR-Codes as an infection vector. They're not fractally complex enough to be dangerous in their own right but they could be used to encourage the naive to follow a link to a web page containing the latest zero day exploit for their computing device. But that's not necessarily parasitic or symbiotic, just a disease.

So instead I'll nominate, "The Gun Thread" as a parasitic meme. It seems like every mailing list or social media community I've ever joined eventually hosts one regardless of the primary topic of the community. There should be some kind of law about the probability of this happening rising towards 1.0 over time.


Cthulhu and Co. as explanation for Fermi's Paradox. I liked it!

But what is your "boring and preferred" explanation of Fermi's Paradox?


So instead I'll nominate, "The Gun Thread" as a parasitic meme. It seems like every mailing list or social media community I've ever joined eventually hosts one regardless of the primary topic of the community. There should be some kind of law about the probability of this happening rising towards 1.0 over time.

Like the Hitler attractor in internet arguments, yes. All ongoing internet discussions eventually get guns, Libertarians, and cats. I don't mind the cats...


Love that book, and I was hoping to use it as a supplementary textbook once upon a time. (Alas...).

At the end, he makes an important point that I've heard from some other scientists. One way to spot a healthy, old ecosystem is to look at the number of parasites and epiparasites it is supporting. For example, I know a lichenologist who looks for lichenicolous fungi. Lichens take a long time to grow, and when they've been around long enough for their parasites to find them (the lichenicolous fungi), then one can surmise that the trees you're looking at are old indeed.

It's an interesting concept that kind of throws a monkey-wrench into modern notions of efficiency, progress, and so forth: that a truly mature system harbors parasites but is not crippled by them. It's an idea whose time mostly hasn't come, unfortunately, because most working ecologists and land managers don't know enough about parasites to see them as anything other than problems.

And no, I won't talk about any industrial-political analogies. That way lies madness...


re Guido @ 153

Nothing new here: Johnatona Swift got there, long ago!


Oh bugger ... HTML scew-up, trying again... Jhonathon Swift ...


julin bond @ 155 You do just realise you've given Charlie another horrible idea for the Laundry? Infected / Dungeon-dimension-summoning QR codes? ARRRGH!


Hm, "Johnatona" would make for an interesting story about cross-dressing early Enlightenment with literary pretentions joining the clergy.

Jhonathon, OTOH, has a subtle Lovecraftian or Dunsanian touch to it, see dholes or bholes or whatever.

BTW, Greg, sorry for this, but as the German saying goes, "wer den Schaden hat, braucht für den Spott nicht zu sorgen"[1].

[1] Somewhat losely translated as: "Whose hit points have taken critical failure damage doesn't have to care for lack of ridicule from the other nerds."

cross-dressing early Enlightenment with literary pretentions

Err, make this:

cross-dressing early Enlightenment women with literary pretentions

Yeah, you are invited to apply the German proverb to me...


It's traditional that whenever you pass comment on someone else's grammar/spelling, your comment must include at least two spelnig misteaks and be missing word.


Vel, yousoally Eye dohned kare dad moch voar sbelleing, id vahs yusd de naise implikazions...


In spite of the relatively early hour, I was very tired when I wrote both of those, so one correction included a new fault ... something programmers should be only too familiar with .....


While I'm not a programmer, I AM all too familiar with that one.

And usually I think correcting other poster's grammar and spelling is a sign of a certain, err, disordered mental equilibrium, err.

And I usually associate it with teachers for German and Paedagogy frequenting "bio food" shops, sending their kids off to Waldorf schools, them having studied being the living embodiment of everything wrong with the German education system, thinking adding and multiplying is everything there is about mathematics, waxing about cognitive deficits in computer users, who think the German plusquamperfect is an error on the part of the speaker, err, let's stop before I get carried away...

Let's just say I have more of a "descriptive grammar" approach on these issues.

It was just that both misspellings made some somewhat twisted sense. And I really think the revelation of Jonathan Swift being a cross-dresser would be somewhat interesting, on a par with Jane Austen being a huge Yorkshireman with a beard like a rhododendron bush, of course a small one, compared to Dorothy Wordsworth's.

That being said, hope you don't feel insulted, it was not meant that way.


You're comparing Jane Austen's hypothetical beard to Dorothy Wordsworth's bush?

OK, I didn't expect that to come up on this thread.


The link did work. And I saw this in your last comment:

"there’s actually another explanation for Fermi’s Paradox that I prefer to this one (if only for boring realism). I’ll leave that for another post."

So what is it?


Damn, I really hate the internet being the ideal carrier for poker. But than, even in real life my irony detector is sufficiently maladjusted I might miss if somebody got my shout-out to

or not. ;)


Fermi's paradox could be explained by economics. Traveling to another solar system might just not be worth the expense. By the time a species has the technology to reach it and the planets therein, it no longer needs them.


Yes, that's part of it, and while I really don't want to derail this thread, the basic idea of spending the equivalent of the South Korean economy and energy budget to send a small mission on a one-way trip to Alpha Centauri is the economic problem. The other issue is in the general category of peak oil. Based on our own history, it appears to be fairly easy to burn through a planet's non-renewable energy reserves, but it appears to be very difficult to figure out how to make a starship whose operation benefits greatly from massive surpluses of energy. The likely outcome of these two historical trends is that, by the time a civilized species is capable of making a starship, it won't have the surplus energy to send it off. This is exacerbated by the fact that the technologies and skillsets needed to make a really small, totally sustainable, light-weight biosphere (aka a starship) are precisely those needed to make a totally sustainable world, and it's a lot easier to live on a totally sustainable world, even if it's hit by a large asteroid or similar cataclysm. Ultimately, I figure that most species burn through their non-renewable energy stocks during the normal "adolescence" of learning to survive as a civilized animal on a planet, and then they are "stuck" on that planet as a mature species for the rest of the planet's existence. Analogies to the current (expensive) state of US collegiate education and the lifetime of paying off student loans after college do come to mind.

This particular post isn't about parasites, but it is interesting thinking about what a mature human civilization might look like, oh, a million years from now. Since parasites tend to accumulate as ecosystems age, if humans continue on our current trend of making ourselves an essential part of Earth's biosphere (along with things like ants and the various descendents of cyanobacteria and their hosts), our descendents are going to be the host for a lot of truly fascinating parasites, all of which will exploit us despite, and sometimes because of, our best efforts.


Ultimately, I figure that most species burn through their non-renewable energy stocks during the normal "adolescence" of learning to survive as a civilized animal on a planet, and then they are "stuck" on that planet as a mature species for the rest of the planet's existence

Did they all magically forget how to use solar power (assuming you can even burn through all the available fissile material that fast)?


No, but the fossil fuels are basically saved solar power. Once you've burned through them, you're stuck with the relatively small amount of usable power you get from the sun (and wind power is powered by the sun too). As for fission and fusion, the general problem there is that you get 20-50 years of power generation, then tens or hundreds of thousands of years of dealing with the resulting waste (and fusion generates radioactive waste as well, though not as much as fission). Unless we figure out some magical way of making radioactive isotopes suddenly inert and safe to handle, fission and fusion appear to be short-term solutions to a chronic energy shortage, however much fuel is available. I'd suggest that innovating on conservation is a more sustainable path in any case, and it's the one most people in the world already follow.


Remember though that our current nuclear power scheme is not even close to the possibilities for the field. The breeder reactor fad of the 1970s fizzled out on two points: anything nuclear attracted NIMBY protests, and people discovered that we had lots of cheap uranium. Should even one of those factors go away we might be getting much more use out of our radioisotopes.

And the solar power limit only exists when your industrial base is trapped down in a planet's gravity well. If you can hang collecting stations in planetary or solar orbit, you can generate arbitrary amounts of electricity.

Humanity currently using about 4E12 watts. Our use for solar power is limited, since terrestrial insolation is only about 1E16-1E17 watts - a lot more than we're using, but there are process losses and we still need to run a planetary biosphere on that. (Contrary to what a corporation would tell you, life support is not optional.) On the other hand, total solar output is around 4E26 watts, so you could run - or melt - a planetary civilization with a tiny fraction of that.


Argh. Sorry for derailing this thread! Parasites, people!

Scott, Agreed, but the problem with climbing out of a gravity well is concentrating enough energy in a small-enough place (e.g. a rocket, or even a launch laser) to boost something to orbit or beyond. That problem never goes away. While I theoretically love the idea of beanstalks, I do believe that a beanstalk would be the gutbucket god plays bluegrass on (here I'm thinking that "tiny" vibrations on a cable tens of thousands of kilometers long are horizontal swings of a kilometer or more while you're spending a week traveling up, not counting twists).

As for fission power, even discounting totally reasonable NIMBY protests (San Onofre is in my local grid, and it appears that the protesters had a better grasp of the plant's engineering flaws than did the plants' PR flacks, because some ex-engineers were among the protesters), the central problem with reactors is what I stated above: they last for a few decades, and they generate a lot of very hazardous, very long-lived waste, whatever their design. Were the plants built to produce for thousands or tens of thousands of years, I wouldn't particularly object, but they're not. Their working life is less than mine, and that makes them unworkable in the long run.


On the continuing assumption that symbiotes are fair game for this thread, I just happened to run across this incredibly cool one via Bruce Schneier:

"The bacterium Vibrio fischeri is a squid terraformer. Although it can live independently in seawater, it also colonises the body of the adorable Hawaiian bobtail squid. The squid nourishes the bacteria with nutrients and the bacteria, in turn, act as an invisibility cloak. They produce a dim light that matches the moonlight shining down from above, masking the squid’s silhouette from predators watching from below. With its light-emitting microbes, the squid becomes less visible."


I’m going to go for the tobacco plant, Nicotinia Tabacum.

I think it has crossed the line from self-defence and become a major parasite on human beings.


In that regard, sugar cane pulls a two-fer: sugar and alcohol. With a side dish of promoting slavery. Talk about a bad actor.


depends somewhat; there are some applications for nicotine as an insecticide. also note nicotinic acetylcholine receptors are quite an interesting target for pharmaceutics, though most of the agents in question don't have nicotine in the synthesis.


What, no love for Asimov's uncharacteristically bleak Hostess?


At risk of being rather late to this thread I'd like to introduce my favorite which is a little different.

Human endogenous retroviruses

For me they beautifully underline just how ubiquitous parasitism is.


Oh do please read the existing comments before posting your own. It stops you looking stupid when you repeat what our OGH has already mentioned at #22.


Damn, I have no idea how I missed that. I can't even claim I was starting to speed read at that point.


grep is your friend

(And if you're reading web pages in an environment where grep is the easiest way to check if a phrase has already occurred, I'll salute you for being hardcore.)


Joined this thread a bit late, and I'm surprised my favourite parasite hasnt been mentioned yet (except possibly for the slave ant thing).

Imagine a virus that infects through wounds in the skin, then finds the nearest neuron and slowly (over months) transport itself to the brain where it begins to modify it. In simpler vertebrates it modifies their behaviour to be more aggresive, while in more intelligent ones (like humans) it also starts a process of dementia which sometimes even make us more likely to bite. At the same time the salivary glands are infected so that when the victim eventually bites someone else there is a high concentration of viruses that gets in direct contact with the wound and the cycle starts all over. The rest of the host i left unaffected.

Good thing Rabies isnt more effective or we would've had something pretty close to a zombie apocalypse at our hands a long time ago.



About this Entry

This page contains a single entry by Charlie Stross published on September 19, 2013 6:15 PM.

Rinse, Drain, Spin ... more Laundry! was the previous entry in this blog.

Commercial interlude is the next entry in this blog.

Find recent content on the main index or look in the archives to find all content.

Search this blog