Biological Reactions to Xenoform Invasion (You guessed it... A Headcrab thread.)

[Pax Ethenica]

Headcrabs, they've been described as cream puffs, target practice and, "That damn thing that gives you a heart attack whenever you see a shadow." But what, exactely, are they? The easiest answer is that they are a parasite, and that while perhaps capable of sexual reproduction are more than likely asexual reprocuders. But... what do we really know beyond the horrors of zombification and advanced physical mutation these creatures are capable of inflicting upon hapless humans?

Behavior and Food Chain Position
Upon their (possible) homeworld of Xen, these creature are, probably at best, a minor pest. Bullsquids, xenomorphic ant lions, and even Vortigaunts seem to treat these creatures with not only outright hostility, but also also impunity. Which leads me to suspect that they are more than likely at the bottom of the Xen ecological food chain. From the brief glimpses of Xen given in HL1, a lot of Xen's plants (or aproximate life form) sport a number of growths similar to the human head in size and/or shape. Headcrabs have no noticable eyes, or the very least they have no noticably large, complex, and dedicated visual organs like eyeballs on thier bodies and could easily mistake a head for its natural food supply.

Soon to come... Infiltration.

 

[Sid Burn]

I wonder if Headcrabs can make Vortigaunts turn to a Headcrab zombie... just wondering.

 

[Danimal]

I wonder if vortigaunts can turn headcrabs into Vortigaunt zombies :|

 

[Emiraly]

*confused*

I wonder if zombies can turn vortigaunts into zombie headcrabs... oh no I've gone crosseyed. :rolling:

 

[ríomhaire]

In HL1 zombies are seen waving their hands over corpses. What's that about, looked like some sorta ritual. Also one is watching TV and his crab was waving its arms all crazy

 

[Emiraly]

In HL1 zombies are seen waving their hands over corpses. What's that about, looked like some sorta ritual. Also one is watching TV and his crab was waving its arms all crazy

The waving was a poorly animated, eating the human corpses. Are you talking about after the residence cascade with the scientist sitting in his chair as he stared at the blinking laptop?

 

[ríomhaire]

Are you talking about after the residence cascade with the scientist sitting in his chair as he stared at the blinking laptop?

Opps . I havn't played HL1 in years so my memory of small details isn't great

 

[Llama]

Hurry up with the next chapter please.

 

[Pax Ethenica]

Infiltration Behavior Expanded

While universally regarded as a parasite I believe that the Headcrab in its natural habitat are, in fact, a symbiote. If the Headcrab were merely a carnivorous parasite, then why would they expend the resources to change the underlying phisiology of human hosts? Why not simply attack the victim and then slowly devour them over time and use the metabolised biomass as fodder for the reproductive cycle? If they were simply parasites, then that would be much more efficient to the inherant parasitic nature of such a creature.

There are two possible theories from least likely from an evolutionary standpoint to the most probable (Please keep in mind, I can be totally wrong about all this, I don't have Valve inside information on enemy concepts. It's s'all speculation.):

Theory 1: The Headcrab needs to commandeer a host organism to survive, and they actively seek out human hosts. If they are unable to latch onto a human or approximate compatable life form, they are unable to feed and reproduce properly, they eventually die.
Cases for: Observed behavior; the Headcrabs seem not only content upon the shoulders of a human host, but they also seem hell bent on getting there. Advanced mutations seen in Opposing Force, where Headcrab infiltration and mutation has reached such a state that entirely new organs are made specifically for defending and attacking at range.
Cases against: Heddy Lamaar (tries to couple or "hump your head" but is unable), most Headcrabs are indeed more mobile unmounted then mounted, as seen in "We Don't Go to Ravenholme" where the player can easily pick off a group of shuffling zombies with ease. There are no advanced mutations in Raven Holme, though enough time has certainly passed for these mutations and full integrations to occur.

Theory 2: Finding themselves in an alien and possibly stressful environment, Headcrabs begin to act upon survival instincts and as such agressively seek out what they percieve as their natural source of sustenance and befinicial symbiosis for protection and improved food gathering for both Headcrab and host. Zombification is simply an unfortunate biproduct of coupling with an alien species, incompatable cellular makeup and biochemistry make for a... messy affair. You have more in common with a catfish than you ever have with a Headcrab in term of genetics, cellular make up, and evolutionary path.
Case for: Heddy Lamaar, a pampered pet, continuously acts agitated and while probably well fed by her owner, continues to try and couple with human hosts as if her/his/its life depended upon it. Raven Holme; Headcrabs are forced to adapt new strains. The fast Headcrabs is a prime example. Normal Headcrabs are ill-suited to catch moving targets, that is a problem, the most clear solution? Make a faster Headcrab strain and see how it does. Also, Poison headcrabs are a good example. Normal Headcrabs are rather easy to kill and can't take down this new form of food fast enough, this is a problem, the most clear solution? Create a strain of Headcrab that is not only hardier than the base genus, but also give it potent toxins based on mutagenic compounds (explained in next chapter) already in the Head Crab organism to weaken the prey first.
Cases against: None that I can think of given my observations. E-mail or post any holes you can think of in my theory.

Coming soon... Mutation

 

[<RJMC>]

since a long time I always thought headcrab are some type of parasites cuz they zombifi creatures

 

[Pax Ethenica]

since a long time I always thought headcrab are some type of parasites cuz they zombifi creatures

I'm going to laugh at you now... Here I go.
BWAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA! Ahhh... Ah-*cough!* Ah-hah... Ah... MUAHAHAHAHAHAHAHAHAHA! :E

 

[DeusExMachina]

The guy is from South America. His first language isn't English....lets not be asshats.

 

[Pax Ethenica]

Of course you're right, I'm sorry. To be honest, someone poked me until I posted something mean.

 

[<RJMC>]

I'm going to laugh at you now... Here I go.
BWAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA! Ahhh... Ah-*cough!* Ah-hah... Ah... MUAHAHAHAHAHAHAHAHAHA! :E

sorry for not be you

oh wait I say sorry?

I should say thanks for not be you

 

[Eejit]

Of course there are alternative explanations for the new Headcrab strains seen in HL2.

For instance one theory is that since they sometimes arrive in Combine-fired shells they could be genetically engineered strain created by the Combine to serve their purposes.

Anyway talking about headcrabs being "forced to adapt new strains" is bad science. For one thing the original headcrabs are still in abundance rather than being out-competed by the newer varieties. Also evolution in nature does not act towards "solutions", evolution occurs as a result of random mutation - there's no 'purpose' to it (except for forced selective breeding as in dogs etc, but that isn't natural.)

 

[Pegcrab]

And how the hell do they breed?

Ach, the mental images are disgusting.

 

[Eejit]

And how the hell do they breed?

Ach, the mental images are disgusting.

Well I assume the Big Momma Headcrab from Xen in HL1 is involved somewhere...

 

[Pegcrab]

Isn't she dead?

 

[BaconIsGood4You]

I always assumed that the fast headcrabs were older (They lose weight and look more beat up, also I assume fast zombies are just farther along in their mutation or whatever it is -one theory is that they tear unneccessary parts off for increased speed-).

The whole evolution theory is poop. I doubt they would be able to evolve that fast. Wouldn't the vort. be evolved if the headcrabs could (assuming that the rapid evolution was due to being from Xen).

I also believe that the poison head crabs are a different species that just came from Xen later. Notice the different breeding habits and choice of host as well as physical differences.

Was the cascade a local thing in Xen, or was it world wide?

 

[TheAmazingRando]

Also evolution in nature does not act towards "solutions", evolution occurs as a result of random mutation - there's no 'purpose' to it (except for forced selective breeding as in dogs etc, but that isn't natural.)

Evolution is not necessarally random. It is true that the mutations are random but Natural Selection weeds out the mutations that are derogatory in it's enviroment, so it is not really random.

 

[Pax Ethenica]

Bad science, well of course it's bad science. With no physical way to test a headcrab, to disect, or to observed... I am forced to use "armchair logic" using my own observations (limited though they are) and draw my own conclusions.

While it is possible that the Combine may have weeded and steered adapation in the base strain of Headcrab, you have to remember that these things have apparently flourished on their own for years, before the Combine arrived.

If they are a super-organism, reproducing exclusively from a single fertile female (or like alien gender as yet unknown) that wouldn't make much sense for a symbiotic or even a parasitic species. The Big Bad Momma Crab described earlier was more than likely a regular headcrab that had absorbed enough biomass to gain the appropriate size and egg-carrying capacity for what is more than likely an aesexual reproductive cycle. The hoardes of headcrabs around her are probably there because the area in which you encountered her is full of the crab's natural food source. The more food in a location, the more organisms you can support in that location.

If you look at it from that standpoint, if Headcrabs are asexual and simply need enough metabolised biomass to support reproduction, then yes... Natural selection would take over, and kill or rarify the unsuccessful random mutations. Anyways, I'm going to get into a possible scenario for such rapid mutation that is related to the gross physical mutation occuring human hosts later.

 

[Pax Ethenica]

Oh, and Fast Headcrabs aren't older headcrabs. The reason they look older is because they simply have more wrinkles... And the reason they look beat up is because those wrinkles catch blood better.

Headcrabs probably breathe through their skin, not that gaping maw at the bottom of their body... If the grip was loose enough to let air pass through, then it wouldn't be that firm... Counterproductive.

For a Fast Headcrab, moving that fast probably needs a lot of oxygen, and how to you get that? You either get bigger lungs, or in the hypothetical case of our skin-breathers... You wrinkle your skin, inscrease the surface area, and thus inscrease the amount of skin that is touching the air while still not having to grow extra weighty under-skin mass that would slow you down.

 

[Pax Ethenica]

Was the cascade a local thing in Xen, or was it world wide?

The Portal Storms decribed by the newpaper in HL2 was world wide, and probably Xen-wide as well.

 

[AzzMan]

I think the different headcrabs we see are just diffferent species. I think of it kinda like snakes. The normal headcrabs would be like any regular snake. Catches what it can, nothing outstanding about it really, maybe lies in ambush to nab unsuspecting prey. Fast headcrab is like a whipsnake or racer, uses speed to catch up with and grab prey before it can react. Poison headcrab would be like, you guessed it, a venomous snake, using its poison to incapacitate a victim for easier zombification.

 

[zinquaff]

You are partially correct, eejit, but natural selection would dictate that all other random experiemnts would have died, thus leaving the poison crabs as the new succesor. Also, if evolution is the answer (I personally think that they are combine enhanced) then saying that it (the evolution theroy) is incorrect is stupid. Do not people and monkeys live toghether even though one is far superior? Thus the original headcrab would live with his poisoned brethern.

Also, to respond to an earlier post, I think that the headcrab would rather live on without attacking anything. I think that attaching to one's head is their best bet of survival (imoblizing victim). I think that they would rather live on to become the size of gronach (the first alein boss from hl1) and thus reproduce its kind by shooting out two mini head crabs at a time.

 

[Eejit]

You are partially correct, eejit, but natural selection would dictate that all other random experiemnts would have died, thus leaving the poison crabs as the new succesor. Also, if evolution is the answer (I personally think that they are combine enhanced) then saying that it (the evolution theroy) is incorrect is stupid. Do not people and monkeys live toghether even though one is far superior? Thus the original headcrab would live with his poisoned brethern.

Ah but we do not compete with monkeys for food. The different headcrab species are actively competing for human hosts/victims.

Survival of the fittest would suggest that the poison and fast headcrabs would out-compete the 'normal', less effective kind.
Just as our ancesters (sorry can remember the name) out-competed neanderthals, leading to their extinction. That is a more accurate comparison than us and monkeys, our species went down their different paths and have largely different habitats and food.

 

[zinquaff]

granted. Perhaps the slower headcrabs are on their way to exitinction. The dinosaurs were not alone when they went extinct. Eventually the headcrab will be phased out, but it is not an instantanius process. There are not enough poison ones to cap all the faces yet.

 

[eber]

In HL1 zombies are seen waving their hands over corpses. What's that about, looked like some sorta ritual. Also one is watching TV and his crab was waving its arms all crazy

are u really so dumb??
1. those zombies were eating !
2. that zombie sitting on the chair was stunned by electricity !
( if you destroyed the trashed computer infront of it , it stopped moving and was dead...

 

[Sid Burn]

are u really so dumb??
1. those zombies were eating !
2. that zombie sitting on the chair was stunned by electricity !
( if you destroyed the trashed computer infront of it , it stopped moving and was dead...

About no.2... I really though it was due to the mutation.

 

[BaconIsGood4You]

The Portal Storms decribed by the newpaper in HL2 was world wide, and probably Xen-wide as well.

No, I mean in HL1. If it was a local event it could explain why there was only normal headcrabs.

I still think that the fast headcrabs are simply older. Since they are apparently superior to regular headcrabs, would they not be in the majority, or at least not such a great minority. A large reduction in body fat (normal headies are chubby little guys) would explain the wrinkles. Also, how would the fast headcrabs survive because of the large increase in demand for energy, and I haven't seen headcrabs munching on any corspes so I assume that they are dependant on a host (also explains large number of them since only a small number would survive while if they depended on getting food limited resources would lead to a population decline). Also, whenever a shell has headcrabs come out, they all are the same kind (at least I have never seen a mixed one). Since I don't think the Combine would care about animal cruelty, they would let the headcrabs stay in a while. Also, the two do not compete/fight at all, where as if they were different species, I believe they would fight because they are so agressive and dependent on a limited number of hosts.

 

[AzzMan]

Or they could just be different species from different parts of xen like I said before.....

 

[Huntoon]

... most Headcrabs are indeed more mobile unmounted then mounted, as seen in "We Don't Go to Ravenholme" where the player can easily pick off a group of shuffling zombies with ease.

I thought the shuffling zombies were the early stage in the process of creating a fast zombie, an "adult" headcrab zombie.

 

[terrorist420]

i thought the fast headcrabs where just adult headcrabs, and the slow zombie ones where youngings, i forget where i heard that

 

[Sid Burn]

i thought the fast headcrabs where just adult headcrabs, and the slow zombie ones where youngings, i forget where i heard that

Maybe its another Xen wildlife species that you never encountered in HL. :smoking:

 

[MiccyNarc]

I believe fast headcrabs are evolved normal headcrabs. They aren't "mature" headcrabs, and fast zombies aren't "matured" headcrab zombies.

Different species entirely.

 

[JoeCLawrence]

To me, it seems like headcrabs are just biological weapons created by the Combine to help subdue planets for invasion. It explains the presence of them on Xen (assuming that Xen was Combine controlled) and why they are launched out of shells by the Combine. Personally, them seem more like to striders than than other Xen natives. Maybe they're both from the same place, like the Combine homeworld or something.

 

[Sid Burn]

To me, it seems like headcrabs are just biological weapons created by the Combine to help subdue planets for invasion. It explains the presence of them on Xen (assuming that Xen was Combine controlled) and why they are launched out of shells by the Combine. Personally, them seem more like to striders than than other Xen natives. Maybe they're both from the same place, like the Combine homeworld or something.

They were not created by the combines... When the combines took over Xen. They used its wild-life against Earth(the reason why they are shelling headcrabs on resistance bases and town)... Anyway, I believe that headcrabs are living in Xen... there's no way it came from the primary planet of the combine.

 

[Pax Ethenica]

Long time coming, but here we go...

Mutation in Core Species in Relation to Gross Physical Mutation of Hosts

While the debate over the differences of Headcrabs strains and thier origins still rages, what I've failed to see is someone pointing out a correlation to the physical changes in the Headcrab's host and the possible changes in the Headcrabs themselves. While I will be going into more detail later, lets get back to basics for a moment...

The stardard, garden variety Headcrab is nothing much, is it? Not really... Probably just a sack of guts and puss walking on four stubby legs, its central body taken up mostly by a single large, fleshy cavity opening up at the underbelly. However! The usual Headcrab Zombie, while not much to look at and easy to kill, is quite a different story entirely.
Two gross (large physical scale) modifications have been made to host body:
The most obvious of which is a large vertical slit cut into the ribcage, abdomen, and then lined with a series of modified ribs or indepentantly grown bony 'teeth'. In HL1, we've seen Zombies feeding on unmutated corpses (we were spared this gruesome sight in upgraded graphical glory in HL2, thankfully), now... In what orfice might this food go into? Of course, into that gaping maw, but where might it go from there? This suggests quite a bit if mutation inside of the host victim as well. Quite a bit of replumbing in the victim is suggested, huh? Well, perhaps not, as we've seen in every regular zombie killed, the victim is face up, and the mouth is constantly open (despite our best post-mortem beatings with a crowbar); the head will not budge. This is probably because foodis passed through the maw, up the esophagus via still a existing gag reflex, and up through the mouth to the waiting Headcrab above.
The second most noticable gross mutation is the hands, long and boney, and from what has been observed, they are incapable of much more than ripping and swiping at prey. It is this mutation (and the "Big Momma" Headcrab in Xen) and leads me to suspect that the Headcrab is more of a symbiont than it is a parasite. Let us, for a moment, assume that a Headcrab has coupled with its natural "prey" upon Xen, such appendages would not only provide an excellant defense (2 Zombies in HL2 slaughter your little band of antlions), but also provide a new source of possible food for the coupled pair in the form of killed attackers (think back to that added mouth!).
These two major physical modifications and mutations coupled with the possible myriad smaller mutations and changes suggest a very involved proccess... That is supposedly done without the Headcrab ever moving around on the body. How can this be?

After the brain and central nervous system of the host victim is compromised (after cranial penetration is achieved by the beak described in HL2), in my hypothesis three things start to happen between human host and Headcrab before a Zombie is formed.
The human host passes out due to either shock of pain in having your skull bored into, fear of attack and imminent death, or simple oxygen deprivation coupled with the physical panic response of extreme pain. After the subject in subdued (as seen in HL2 Chapter 3 Route Canal), the Headcrab actualyl motions a definite humping-like action.
I think, personally, that some form of mutagenic substance is then pumped through the beak after the cognitive and central nervous systems of the host are comprimized by the Headcrab feeding upon the first few inches of colarie-rich fatty brain matter. The billions of blood vessels suddenly opened up through the ruined brain matter are a prime channel for our hypothetical mutagenic puss to be pumped through the rest of the body. During this stage, new blood vessels are formed, and the barely dead body suddenly gets a biochemical jumpstart from the mutagen (also this substance can probably substitute as a possible approximate fat reserve for the Headcrab during hard times), cell start to divide, and new metabolic proccesses begin, absorbing the organs and cells that this new and very alien "body plan" do not call for. The absorbed organs are broken down and used as fuel to grow out the hands, and with the loss of the these organs, the chest and stomach cave in, and then you have a convieniant place to put your new mouth.
During the thrid stage of inactivity, any calories or substances matabolically compatable with the Headcrab is then coverted metabolized by the Headcrab itself, to replenish its stores of mutagen, not to mention a possible body fat it might use later on for the reproductive cycle. Also, during this late stage, the body of the victim is laying out the blood vessels and lymphic connects for the slow absorbing of the body, hence its physically depaltidate and anemic state. At this point, the Headcrab starts to slowly devour the body when it needs to do so in order to keep itself alive.
In Xen, we do not know what the natural result of such a coupling might be; however, I personally think that the result is less messy, painful to watch, and painful to recieve.

 

[Pax Ethenica]

Going to put up more later. My fingers are on fire from typing all of this up in under 45 minutes.

Edit: Lovely! My brain just exploded... Now if I can just remember where I put the 409, and clean up the brain splatter I could up more tonight. Damn you irony!

 

[Sid Burn]

Long time coming, but here we go...

Mutation in Core Species in Relation to Gross Physical Mutation of Hosts

While the debate over the differences of Headcrabs strains and thier origins still rages, what I've failed to see is someone pointing out a correlation to the physical changes in the Headcrab's host and the possible changes in the Headcrabs themselves. While I will be going into more detail later, lets get back to basics for a moment...

The stardard, garden variety Headcrab is nothing much, is it? Not really... Probably just a sack of guts and puss walking on four stubby legs, its central body taken up mostly by a single large, fleshy cavity opening up at the underbelly. However! The usual Headcrab Zombie, while not much to look at and easy to kill, is quite a different story entirely.
Two gross (large physical scale) modifications have been made to host body:
The most obvious of which is a large vertical slit cut into the ribcage, abdomen, and then lined with a series of modified ribs or indepentantly grown bony 'teeth'. In HL1, we've seen Zombies feeding on unmutated corpses (we were spared this gruesome sight in upgraded graphical glory in HL2, thankfully), now... In what orfice might this food go into? Of course, into that gaping maw, but where might it go from there? This suggests quite a bit if mutation inside of the host victim as well. Quite a bit of replumbing in the victim is suggested, huh? Well, perhaps not, as we've seen in every regular zombie killed, the victim is face up, and the mouth is constantly open (despite our best post-mortem beatings with a crowbar); the head will not budge. This is probably because foodis passed through the maw, up the esophagus via still a existing gag reflex, and up through the mouth to the waiting Headcrab above.
The second most noticable gross mutation is the hands, long and boney, and from what has been observed, they are incapable of much more than ripping and swiping at prey. It is this mutation (and the "Big Momma" Headcrab in Xen) and leads me to suspect that the Headcrab is more of a symbiont than it is a parasite. Let us, for a moment, assume that a Headcrab has coupled with its natural "prey" upon Xen, such appendages would not only provide an excellant defense (2 Zombies in HL2 slaughter your little band of antlions), but also provide a new source of possible food for the coupled pair in the form of killed attackers (think back to that added mouth!).
These two major physical modifications and mutations coupled with the possible myriad smaller mutations and changes suggest a very involved proccess... That is supposedly done without the Headcrab ever moving around on the body. How can this be?

After the brain and central nervous system of the host victim is compromised (after cranial penetration is achieved by the beak described in HL2), in my hypothesis three things start to happen between human host and Headcrab before a Zombie is formed.
The human host passes out due to either shock of pain in having your skull bored into, fear of attack and imminent death, or simple oxygen deprivation coupled with the physical panic response of extreme pain. After the subject in subdued (as seen in HL2 Chapter 3 Route Canal), the Headcrab actualyl motions a definite humping-like action.
I think, personally, that some form of mutagenic substance is then pumped through the beak after the cognitive and central nervous systems of the host are comprimized by the Headcrab feeding upon the first few inches of colarie-rich fatty brain matter. The billions of blood vessels suddenly opened up through the ruined brain matter are a prime channel for our hypothetical mutagenic puss to be pumped through the rest of the body. During this stage, new blood vessels are formed, and the barely dead body suddenly gets a biochemical jumpstart from the mutagen (also this substance can probably substitute as a possible approximate fat reserve for the Headcrab during hard times), cell start to divide, and new metabolic proccesses begin, absorbing the organs and cells that this new and very alien "body plan" do not call for. The absorbed organs are broken down and used as fuel to grow out the hands, and with the loss of the these organs, the chest and stomach cave in, and then you have a convieniant place to put your new mouth.
During the thrid stage of inactivity, any calories or substances matabolically compatable with the Headcrab is then coverted metabolized by the Headcrab itself, to replenish its stores of mutagen, not to mention a possible body fat it might use later on for the reproductive cycle. Also, during this late stage, the body of the victim is laying out the blood vessels and lymphic connects for the slow absorbing of the body, hence its physically depaltidate and anemic state. At this point, the Headcrab starts to slowly devour the body when it needs to do so in order to keep itself alive.
In Xen, we do not know what the natural result of such a coupling might be; however, I personally think that the result is less messy, painful to watch, and painful to recieve.

Hmm... that explains it all...