Barnacle

"They were only able to coerce it into latching onto organic surfaces."

- Black Mesa scientist

The Barnacle, its full name being Cirripedia donaldsonia, is a stationary ceiling-dwelling alien, notable for its unique method of catching prey using its sticky "tongue".

Overview
Physically, Barnacles resemble little more than a large mouth full of sharp teeth and a thin, but long muscular string-like appendage that secretes a very strong natural adhesive that has the capability of bonding to masses such as adult humans with ease. This appendage combines the functions of a tongue and tentacle, which can be retracted or extended to hang at near-floor level regardless of the animal's height from the floor. Barnacles are only aided with somatosensors (can only sense touch), and are not capable of registering audial or visual occurances. The limited sensory capability of the Barnacles results in, on occasion, the incorrect registration of inorganic objects as prey. In such an event of fruitlessness, they dispose of the catch by releasing it, showing they can disolve their own adhesives, if need be. The creatures attach themselves to ceilings or the undersides of overhangs, from which they lower their sticky tongues. Although Barnacles can be found in a wide array of environments, they seem to prefer damp areas. Curiously, while many Barnacles can be found infesting the Black Mesa Research Facility, few are encountered on Xen.

Barnacles are relatively weak; 5 shots from a 9mm pistol will kill them. They are most easily dispatched from a distance, although players who become ensnared are usually able to kill them before being consumed. The Barnacles are weak against the crowbar, which in both games, kills them in a single hit (except in Half-Life: Day One, where four hits are required, which will be fatal for the player). In any game, attacking a barnacle which is high up with a crowbar is generally a bad idea, as you will take fall damage as well as the barnacle's attack. In Half-Life (Method not tested in other games), an undetonated hand grenade will kill a barnacle instantly. When killed, Barnacles typically disgorge bones and other remains of recently-consumed victims.

In Opposing Force, a scientist refers to removing a Barnacle from its "point of gestation". This suggests that a Barnacle will naturally spend its entire life attached to the spot where it was born. However, it is unknown exactly how Barnacles reproduce, or how the offspring spread to different environments and attach to ceilings. Real Barnacles use mobile larval stages and ocean currents to disperse, but no equivalent life history stage has been observed for Half-Life's Barnacles (as a sidenote, the scientist's use of the term "gestation" may be incorrect depending upon how Barnacles reproduce and disperse). However, it is known that they are attached very firmly and permanently, as evidenced by their continued attachment after death. In Half-Life 2 and its episodes, the Barnacle has a "second mouth" that it uses to eat. When killed, the mouth hangs out from its body, whereas the original Barnacle has small inner teeth inside its thick "lips".

Behavior and skills


Barnacles are relatively simple creatures. They do not appear to possess any degree of intelligence - instead of actively hunting prey, they feed by reacting to external stimulus, in the form of animals which come into contact with the Barnacles' tongue. Although the creatures do not demonstrate any intelligence in hunting, they possess an uncanny ability to attach themselves to ceilings overlooking thoroughfares frequented by potential prey, although some do seem to hide in corners far away from routes used by prey (the logical explanation for this is Barnacles in less adequate conditions die out, while luckier creatures flourish). Similarly to real Barnacles, they typically occur in groups or colonies. These are found throughout the entire Half-Life series, and the player often encounters small areas populated with large numbers of Barnacles, which do not seem to be in competition with each other.

Trapping and feeding abilities
When an object, living or otherwise, comes into contact with the tongue, it somehow latches onto the object (the exact mechanism behind the tongue is unknown). The Barnacle then retracts its tongue, drawing the object towards its mouth. Upon reaching the mouth, the object is quickly evaluated by the Barnacle: objects considered edible by the Barnacle are crushed and consumed; inedible objects are released. Barnacles appear to be capable of killing and digesting a human being within only a few seconds (literally swallowing it), stripping the skeleton of flesh and spitting out indigestible bones. As the Barnacles are never seen moving, it can be assumed that their food requirements are relatively low and that they can survive for extended periods without food, perhaps explaining their sedentary lifestyle.

In the original Half-Life, humans become immobilized when caught by Barnacles—although they struggle when wrapped in the creatures' tongues, captured humans appear to be incapable of fighting against the Barnacle when they reach the mouth, even though they are clearly still alive. It is possible to save a NPC from a Barnacle by killing it before he or she is consumed. The NPC will then simply drop, unharmed.

In Half-Life 2, Barnacles take a few moments to differentiate between edible and inedible material. Consequently, objects such as tires, barrels or pieces of wood can be used to "distract" a Barnacle and allow a player to easily slip past it. In a similar fashion, by setting alight an explosive barrel at the right moment, a player can kill a Barnacle attempting to eat it (or even several closely-placed Barnacles). It also seems that the Barnacle tries to wrap its tongue around the target tight enough to break bones and kill it. This is based on the observation that birds as well as Resistance or Combine troops die before they even reach the main body, merely by virtue of being caught. Turning on closed captions and then being captured by the Barnacle reveals the sound file is called "Barnacle Neckbreak"; also, in a Half-Life 2 concept art, a Barnacle's tongue is seen wrapped around Gordon's neck, trying to strangle him. Gordon Freeman is unaffected by the tongue's crushing attempts, probably due to his HEV Suit's neck-covering extension. An alternative explanation might be that tongue incapacitates the Barnacle's prey by means of some sort of paralyzing neurotoxin.

It is interesting to note the manner in which a Barnacle in Half-Life 2: Episode One deals with a Zombine: after capturing a Zombine, the Barnacle will only eat the attached headcrab, while the beheaded body is dropped. On the other hand, Barnacles have been recorded consuming the entire body of unaffected Combine soldiers. This could be considered evidence that Barnacles dislike the taste of rotting or decomposed flesh, and would be consistent with their rejection of decomposed bodies thrown at them by the player. A glitch might occur where the Barnacle kills a zombie of any type and throws the body to the ground. However, it will continue to pick it up and discard it until the body is moved.

In Half-Life 2: Episode Two, Barnacles are seen trapping and eating Antlions. They are also seen trapping Acid Worker Antlions, but as the Worker explodes as it is bitten into, this invariably results in the death of both parties.

An interesting fact is that the Barnacle will only eat what it identifies as a humanoid-type creature (Human, Vortigaunt) if it latches onto the head. If it latches to the waist, leg, hand, etc. the Barnacle drops the body as if inedible, possibly because of the difficulty in consuming it in such position, or it doesn't recognize the shape due to latching on part of a body that is not the head or neck.

Behind the scenes

 * According to Gabe Newell, the Barnacle was created through gameplay as a way to constrict movement in dark areas of the Black Mesa Research Facility, suggesting its creation is quite recent in the game's development.


 * The Coast chapters of Half-Life 2 were originally to feature a Barnacle variation, the Sand Barnacle.


 * It appears that barnacles originally had ability to strike targets in Half-Life.

Trivia

 * It is possible to get an achievement called "Barnacle Bowling" by killing a large group of them via explosive barrels.
 * The top of the Barnacle can be seen in the Barnacle weapon worldmodel from Opposing Force.
 * In real life, the barnacle (or Cirripedia) is an arthropod related to crabs and lobsters.
 * It is possible the Barnacle was inspired by a similar creature in Sierra's Space Quest III. Native to a small rock cluster of Planet Phleebhut, they had a similar method of grabbing things with their tongues and determining whether or not something was edible (Terminator Robots, while not edible, would still be destroyed).
 * In Garry's Mod it is possible for the barnacle to eat Antlions, or Antlion Guards. When consumed, any objects it eats will simply float through the ceiling it is attached to.
 * Though in Half-Life the barnacle can only attach to organic surfaces, in Half-Life 2 it will latch onto barrels, tries, and other man-made objects.
 * If a Poison Zombie gets eaten by a barnacle in Half-Life 2 or the episodes, the game will crash because they never appear on the same map without cheats. However, in Portal or Garry's Mod it won't because you have to spawn them.

List of appearances

 * Half-Life: Day One
 * Half-Life
 * Half-Life: Uplink
 * Half-Life: Opposing Force
 * Half-Life: Blue Shift
 * Half-Life 2
 * Half-Life 2: Raising the Bar
 * Half-Life 2: Episode One
 * Half-Life 2: Episode Two