Xenomorph

## Exposition

The **Xenomorph XX121**, better known just as **Xenomorph** or the "**Alien**", is an extraterrestrial hive-based endoparasitoid species with a multi-staged life cycle, possibly originating from the planet **Xenomorph Prime**. One of the deadliest of all known alien species, these creatures require a host organism in order to reproduce. The appearance of the Xenomorph can vary depending on the host in which the embryo is implanted. The Human phenotype is generally around 7–9 feet (~ 2.13 - 2.74 meters) in height and roughly 181.43 to 272.15 kilograms (400-600 pounds) in weight, with a long, muscular tail and large, curved, oblong head. The Queen of this species is generally twice as large (although some Queens have been shown to grow even larger, some surpassing 30 meters in height if given time) and possesses superior speed, strength and intelligence compared to her common offspring.

## Intelligence

Most Xenomorphs appear to possess an intelligence level equivalent to that of a typical primate. It's well within their capabilities to learn relatively quickly, gathering information and making advantageous use of their environment. Although they do not demonstrate Human and Yautja-level intelligence as a species (such as abstract reasoning, introspection and technological advancement), their Queen appears to possess considerable acumen in her social behavior and manipulation of Human technology, such as cutting the power of the LV-426 colony and operating an elevator. While it may take considerable time for them to learn how to operate machinery, other Xenomorphs have displayed fast reasoning and the capacity to find creative, counter-intuitive solutions to problems, as exemplified by a group which, after noticing that they were being contained, intentionally murdered the weakest so that the acid of the Xenomorph's blood would eat through the floors.

As the adult Xenomorphs are known to inherit physical characteristics from their hosts (for example, when a Yautja was infected, the parasite later developed into a "Predamorph" or "Predalien") it is possible that the intelligence level of the creature may be influenced by its host as well. Furthermore, being an eusocial species, it is possible that the intellectual capacity varies for each different caste.

Xenomorphs have demonstrated little emotion, though they are not completely devoid of fear, such as when they are in the presence of fire, which they are vulnerable to. They have also been shown to communicate pain through shrieks or screams when attacked.

## Anatomy

A Xenomorph is equipped to be the perfect killing machine. They possess an exoskeleton much like that of a lobster, impenetrable to everything but the most powerful Human firearms (12-gauge shotguns, Pulse Rifles, and stanchion launchers are quite effective). Ash claims the creature's skin is made from "protein polysaccharides", so this would imply a substance similar to chitin. He also says the creature replaces its surface cells with polarized silicon, which is a very inert, heat resistant, and flexible polymer. This allows these creatures great environmental resistance. However, they are vulnerable to sudden, massive changes in temperature. It's been demonstrated that they can be destroyed by immersion in molten lead followed by sudden cooling with fire sprinklers, causing their silicon shells to shatter.

Attached at the ends of both of their arms are a set of long fingers and shiny, black, extremely sharp claws capable of slashing through almost anything within their grasp. Their tail is long and flexible. Some, though not all, individuals also have ridges on top, and a serrated toxic tip at the end of the tail to lacerate enemies.

They stand at around 7 feet tall (~ 2.13 m), averaging in anywhere between 140 and 180 kg; although size may vary wildly depending on the host chosen, as seen for instance with the "Jock-Xenomorph": a gigantic creature spawned from a Paladian host.

## Abilities

The adult Xenomorph is a living weapon, noted for their ferocity and deadliness in any condition. Once fully matured, they have great physical strength and agility. They are masters of stealth; a favored method of acquiring prey is to wait in a dormant state until an appropriate victim strays near, and then drop down silently from behind or use their tail to impale whoever walks by. The prey is generally blind to the fact that a Xenomorph is present, due to its propensity to camouflage itself within its nest walls or the surrounding artificial environment, given their biomechanical-like appearance. The Xenomorphs will also use their pitch black carapace to their advantage, lurking in the shadows whilst waiting for prey to stray too close.

Xenomorphs are shown to be able to take extreme amounts of physical damage that would kill any earthly life form. An example of this is a Queen that survived a multi-ton exo-suit falling on her from over 30 feet. Xenomorphs are capable of surviving with limbs shot off, stabbings and even shots through the head (though total decapitation kills them).

Adult Xenomorphs are quick and agile, and can clamber along ceilings and walls: a skill they exhibit freely whether they are evading others, attacking, or hunting. They can survive in extreme temperatures, are well-adapted to swimming, can respire in harsh atmospheres, and can survive in vacuum for indeterminate lengths of time. Their movements tend to be silent, and they do not radiate heat as their exoskeletal temperature matches the ambient temperature. They also salivate profusely. This saliva is not acidic, though some Xenomorphs do have the ability to spit acid, which may come from their stomachs, a special gland somewhere in their throats, or acid pouches lining the head. This can be used to blind victims, much like a spitting cobra.

Due to the absence of clearly visible eyes, it is possible that the creature uses echolocation to see its environment, much like bats. It may be for this reason that Xenomorphs hiss almost constantly, though there is evidence that they can detect light and darkness as well. Xenomorphs may be able to find their prey through electro-reception. This is the method sharks use to detect even the most hidden prey. Creatures with the electro-reception sense can detect the electromagnetic field all animals produce, allowing them to locate their prey by its heart beats, even if the prey is immobile. This would explain how Xenomorphs always know where the Humans are. Furthermore, the Xenomorphs can also detect whether a potential host is already infected, likely by sensing pheromones.

## Vulnerabilities

Xenomorphs, in all stages of their life cycles, have been said to have vulnerabilities to heat. The use of molotov cocktails and flamethrowers constitutes an effective technique to drive them off. The only Xenomorph not vulnerable to fire is the Predalien, which can secrete a layer over its body that cannot be ignited, although they are still visibly pained by temperature extremes, such as liquid nitrogen.

A rapid succession of extremes in both high and low temperatures apparently causes a thermal shock effect on a Xenomorph's exoskeleton. Xenomorphs are capable of adapting themselves to cold environments with little discomfort. However, the alien Queen is particularly vulnerable to fire, for unknown reasons.

Depending on the circumstances, Xenomorphs are shown to be both invulnerable and vulnerable to small firearms, ranging from 9mm to 5.56mm. This is seen when Vasquez and Lt. Gorman find themselves trapped in the ventilation between advancing aliens coming from both directions. Gorman fires with his pistol on one of them with no effect at all, instead it looks like the ammunition bounces off (presumably from the head carapace). In another occasion, however, Vasquez holds an alien at gun point and fires her pistol at the head, which apparently goes through and the alien rattles away, obviously damaged. High-caliber firearms, with the explosive rounds of a M41A Pulse Rifle may cause the creatures to detonate. High-energy beam weapons, such as the plasma weapons used by Yautja, appear to be the best way to kill the Xenomorphs, though pulse rifles appear to be the best way to repel large hordes of them since they can fire non-stop and are not prone to being destroyed like the plasma weapons.

Xenomorphs are not invulnerable to melee weapons, although such equipment is likely to be destroyed upon contact with their acidic blood.

## Acidic blood

The body fluid of all Xenomorphs appears to be a highly concentrated acid. It is frequently referred to as "acid blood", although it isn't clear whether or not it's used to carry any nutrients through the body.

It is somewhat unlikely that this fluid carries oxygen for a few reasons: the first being that the Xenomorph has been known to survive in vacuums such as space (for short periods of time, at least). The second being that Bishop mentions that the fluid loses its acidity shortly after the creature's death due to oxidation. On the other hand, this is plausibly unimportant as oxidation is a term in chemistry used for the loss of electrons rather than a reaction with oxygen. All acids are oxidized no matter what they react with, therefore this has no bearing on blood carrying oxygen.

The "acidic blood" is able to dissolve through almost everything except the Xenomorph's body. The creature itself apparently knows how corrosive its "blood" is, as one flicked it at a charging Yautja, and it has been used to escape cages (by killing a "brother"). Some specially-treated Yautja weapons can resist this acid, although how long exactly is unknown.

It has been often theorized that the Xenomorph "blood" may serve no function other than defense, being a liquid stored under the creature's skin that causes great harm to whoever succeeds in harming the Xenomorph. It remains possible, though, that the acid serves some function in the alien's metabolism, perhaps even as an actual blood system analogue. One possibility is that it may be an extreme analogue of stomach acid, and likewise serves to digest food. In that case, the Xenomorph's digestive system would be spread like a circulatory system throughout its body: the acid is so powerful that anything it consumes is immediately dissolved and the remains distributed over its body, with the extremely resistant walls of the "acid vessels" somehow allowing nutrients to be absorbed.

## Genetic adaptation

Due to horizontal gene transfer during the gestation period, the Xenomorph also takes on some of the basic physical attributes of the host from which it was born, allowing the individual alien to adapt to the host's environment more efficiently.

Through experiments, it was discovered that the embryo attaches itself to a major artery of its host, to get nutrients as it grows. It is presumed that the DNA from the blood it acquires infuses itself with the embryo's DNA to make up for its lack of genetic structure.

It may take on a thicker, bipedal form with a darker exoskeleton if it comes from something that stands on two legs, such as a Human. When the host is a four-legged animal, it may take on a more slender, sleeker appearance, where it too moves as a quadruped, and has a more reddish/orange-colored exoskeleton. It may also take on some facial features of its host (such as mandibles when implanted in a Yautja). Predaliens (Xenomorphs spawned from Yautja hosts) have a yellow-green partial skin covering their exoskeletons.

Furthermore, it is conceivable that it derives some level of intellect from its host. The quadrupedal Xenomorph seems easier to trick than bipedal ones, and the Predalien appears to have a better understanding of weapons being used against it.

## Life cycle

The Xenomorph is born in egg form, laid in place by the hive's Queen, through the use of a detachable ovipositor. The egg is thick and gelatinous, usually with several membranes attached to the outer layers. It can take nutrients from the ground to support the creature inside. The egg has vein-like structures running through it, showing that it is actually a living creature, sometimes known as an **ovomorph**.

The Xenomorph hatchling - called a facehugger - is protected by a thick fleshy layer at the top of the egg, where the "shell" peels open when the facehugger senses creatures nearby. The sense that detects suitable organisms has to be very specific in what it chooses to respond to. Perhaps this is why it takes so long to open: various sensory organs study the approaching organism. It seems to be capable of distinguishing synthetic life from organic life.

Sometimes Xenomorph Queens can lay eggs that contain up to four facehuggers.

#### Facehugger

After the egg opens, the **facehugger** emerges and seeks out a nearby life form, latching onto its face, wrapping its tail around its airway, and implanting the Xenomorph embryo(s) by sticking a tube down the host's throat. This is seen sometimes when a facehugger is contained in water or lunging at a soon to be host.

It will coil its tail tighter around the airway to prevent premature removal, and an attempt to sever the fingers found that facehuggers possess the same acidic blood as an adult Xenomorph. The facehugger supplies oxygen to keep the host alive during the impregnating process. Once the embryo(s) has been implanted, the facehugger falls off, curls up, and dies.

Hosts usually fall into a short coma and wake up ravenously hungry. This can be explained as the embryo needing an immediate source of nutrients for its progression into the next stage of its life. Hours might pass between the host waking and their time of death. Yautja live the longest as a result of an extended incubation period. The reason for this is likely due to the genetic complexity of the host. The incubating chestburster requires more time for mitosis and cytokinesis due to the morphology of the Predalien.

However, in some cases, the hosts will awake not gradually but suddenly - just in time to be conscious of the chestburster's push out into the world. Their state of normalcy will last only seconds or minutes.

It's also proven that when a host awakens, there is some sort of a memory lapse in which they don't remember anything that has happened to them. This short-term memory loss is most likely a result of the temporary oxygen deprivation caused by the facehugger's tail, as it asphyxiates the host.

Different facehuggers are known to exist, including some highly abnormal ones. The **royal facehugger** will give rise to Queens or to members of the Praetorian caste, the latter which may be promoted to Queens later on. However, there's also a poorly-known caste of **giant facehuggers** which are also known as **queen facehuggers**, but don't seem to be related to Queens directly. Unlike regular facehuggers, these giants don't seek to impregnate hosts, but merely protect the ovomorphs. They may use their legs and tail to immobilize potential hosts, allowing regular facehuggers to latch onto the victims' faces and impregnate them.

Another highly aberrant form is the **Infectoid** facehugger, which doesn't implant an embryo, but rather fuses itself to the host's body, transforming the host into an undead zombie-like being, linked to the aliens' hive mind.

#### Chestburster

After attaching itself to a vein and gestating in the chest cavity, Xenomorph infants - called **chestbursters** - push and chew through the host's chest, causing severe pain, blood loss, shock and death. The host's rib cage is cracked open, bones bent outward. No one has survived this process other than Emmett Martens, who was fitted with an artificial body following this encounter. However, was cryogenically frozen after she was cloned, and then had it surgically removed. It was also revealed that high amounts of stress can actually make the chestburster more frantic. This causes it to push and chew through the chest at a faster pace, therefore emerging slightly earlier than normal. On one occasion, the chestburster erupted out of the head of a host Human instead of the chest.

It is suggested that the removal of the chestburster would still lead to the death of the host due to the remaining alien tissue acting like a malignant tumor, in effect developing into a fatal cancerous growth.

At this stage, the Xenomorph is small, limbless, and very vulnerable. Among other possibilities, its neck can be snapped. It needs to get to a safe area so it can reach its next life stage. It moves with its long tail, and can coil up and jump. It cannot climb on walls or ceilings, but despite these drawbacks it can traverse an area with astonishing speed.

In some cases, they turn into a cocoon, though this could be a subspecies. The common assumption is that the alien molts, grows legs, and develops much like a tadpole turning into a frog. Another common theory (the most accepted one) is that chestbursters shed their skin upon growing, as shown when Brett picks up a chestburster skin he found on the floor in an area the chestburster took shelter in.

At very rare times the chestburster emerges after the host has already died, which has been observed in an ox. Why the ox died after it was implanted is unknown; though the most likely reason would be due to a combination of the stress of implantation coupled with the poor health of the animal. It is seen to be riddled with parasites and presumably spent much of its life in the harsh environment of Fiorina "Fury" 161. Strangely, in this circumstance, the chestburster lived. This was also seen after the Empress killed a Predator and the chestburster survived.

In some cases, morphological traits acquired from the host may already be visible in the chestburster stage, for example: a chestburster born from a Yautja will already display the characteristic mandibles of the race. Some chestbursters already have legs when they emerge, including the royal chestburster and the "Runner".

A Xenomorph in this stage is known as the **bellyburster**, which erupts from the host's abdomen, rather than chest. These seem to be formed when the host is pregnant, and the alien embryo develops inside the womb, presumably feeding on the fetus or multiple fetuses. A Predalien has been observed to impregnate several hosts with multiple embryos each through the mouth, which later gave rise to bellybursters. Since multiple bellybursters can develop inside a single host's womb, they can be used as an efficient way for a young future-Queen to establish a new hive faster.

#### Adult

Little is known about the transformation that occurs between the chestburster and **adult** phases. As already stated, the Xenomorph appears to molt before reaching maturity. Maturity is reached in a few hours, and involves a dozen-fold increase in mass, which would presumably require some form of nourishment. In the *Nostromo*, Ripley comes across a food locker that had been raided, apparently by the Xenomorph to get food.

When the first Drone encountered on record was born in the *Nostromo*, it had a smooth, long head, and an upright-standing body. It had no visible eyes, a tail, and strange spines protruding from its back. However, many years later on LV-426, the same species was found, but they looked slightly different. The head was no longer smooth, but ridged. One theory is that the smooth-headed Xenomorph was a Drone, and the ridge-headed Xenomorphs were Warriors. This is supported by the fact that the alien aboard the *Nostromo* built a nest, which only Drones can do since it is part of their job in the colony.

Another widely accepted idea, however, is age - the Xenomorphs found on LV-426 were more than a few days old, while all of the others encountered were less than a day old. On the other hand, some hives seem to have a distinct coloration for each caste, in which the Drones are black and the Warriors are a very dark blue; the color difference indicating that age is not a factor.

Another Xenomorph was encountered on an expedition to Antarctica. These Warriors were less humanoid and sometimes walked on all fours. Their tails were longer, with a large, curved barb at the end. The head was smooth but much shorter than normal. It is important to note, however, that this particular Xenomorph hive was grown by the Predators, who introduced a hormone with unknown effects into the Queen's system.

As the Xenomorph has been shown to be an extremely adaptable organism, which lays hundreds of eggs, develops quickly and is highly efficient at altering its own genome to better fit the environment (absorbing traits from its hosts), it's very likely that some phenotype Xenomorphs are simply the result of genetic variety between different populations, which evolve very fast.