Just like the original 1979 Alien film, the horror of the xenomorph’s reproductive cycle all
starts with eggs, a.k.a. ovomorphs. Ovomorphs are laid by a queen, and they are far more than
meets the eye. In fact, they have a symbiotic relationship with their in vivo facehuggers, and are
able to “‘sense’ or otherwise detect when a potential host creature approaches.” This way they
can open their tops, flower-like…
The facehugger is the second stage of the xenomorph’s life cycle, and is, at its core,
a delivery system for inserting the xenomorph’s DNA into a host. The facehugger isn’t so
much about delivering sperm, like real spermatophores are, but is instead used to deliver a knot
of cells (basically an embryo) through the mouth of the host. It executes this goal by clinging
to the host’s face and tightening its tail around the throat to minimize oxygen moving to
the brain, keeping the host alive but unconscious. (It also apparently delivers
“a cyanose-based paralytic chemical” to help sedate the host.) Once the ‘Morph DNA
has been delivered via a proboscis down the throat, the facehugger detaches and dies.
Once the facehugger has delivered its knot of xenomorph cells into the host, those cells
have what is known in-universe as the “DNA Reflex.” This DNA Reflex works much like real-life
lateral gene transfer: meaning the xenomorph’s cells release their DNA and inject it into
the host’s cells. (This, incidentally, is the reason xenomorphs take on the characteristics
of their hosts.) Those cells containing hybrid host-xenomorph DNA then multiply uncontrollably,
much like cancer, and grow into a chestburster, which, y’know…
After the Alien burst out of it's host, it can differ in size but it will have an average
body size of one meter. In Alien Covenant exist a version of the alien forms which is white
the fresh born alien of this life form is very animal like with agressive behaviour
and has long sharp thorns on it's back and on the end of it's tail. It is very fast growing.
On the other side the black alien form is more human like in it's shape but the appearence differs alot.
It has long arms also thorns and a very long tail.
Neomorphs are a subspecies of Xenomorph encountered by the USCSS Covenant. There are
many noticeable differences between the two species for example Neomorphs are far more animal
like and almost always feed on their prey after they kill it unlike Xenomorphs. The Neomorphs
animal-like nature could suggest a lower intelligence. Neomorphs like the Deacon alsolack a inner
mouth. Neomorph's enter their host's body through spores, normally through the ear or nose, and
gestate inside the hosts blood. These spores are released by a fungal pod growing on "Paradise" that
have been altered by theblack pathogen. Unlike Xenomorphs they can erupt from various parts of
the body and have been observed to do so after a matter of hours since firstimplantation. The emerged
creatureis known as a Bloodburster before quickly growing and becoming an adult Neomorph
Once a chestburster has done its thing, i.e. explode out of its host, killing it — why
xenomorphs would technically be considered parasitoids rather than parasites — it runs
off somewhere to grow into an adult. This growth process, from tiny burster into full-blown
gonna-eat-cha adult, happens extremely fast, on the order of hours. Once a xenomorph is full grown,
you’re talking about a seven-foot-tall terror armed with a protective exoskeleton, deadly
teeth, a deadly barbed tail, deadly claws, and a deadly set of just about everything else.
They also apparently have superhuman strength, quickness, stealth, and general combat
abilities. Plus they have those inner mouths, which are fictional correlates of the pharyngeal jaws
of a moray eel, but about one billion times as freaky.