Barnacle

The Barnacle (taxonomic designation: Cirripedia donaldsonia, or "Donaldson's Barnacle") is a stationary ceiling-dwelling alien creature, which is most notable for its unique method of catching prey using its sticky "tongue."

Overview: A Barnacle is little more than a large mouth full of two rows of sharp teeth, with a long string-like appendage dangling out of its maw. The Barnacle uses its "tongue" to snare and lift prey items; the appendage is strong enough to support the weight of an adult human. On its tongue is a very strong natural adhesive (such as cilia/setae) that can bond to whatever it comes in contact with. Barnacles cannot differentiate between living and inorganic items that become stuck to their tongues, and can be tricked into hauling in barrels, pallets and other debris commonly found in their vicinity. Upon attempting to consume these items, the Barnacle will find them unpalatable and release them. The ability to turn their tongue's stickiness on and off at will suggests that the Barnacle tongue adhesive is actually formed by cilia or setae (tiny hairs or bristles, as on a gecko's foot) rather than a sticky chemical. By this model, when potential prey comes in contact with the tongue, the Barnacle feels it and directs the cilia/setae to activate into their adhesive form, and conversely to deactivate into their normal relaxed form if the prey turns out to be unsuitable. If the Barnacle is killed, the cilia/setae are permanently deactivated also, which is why dead Barnacle tongues are not sticky. Barnacles 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 when compared to most enemies: 4-5 shots from a 9mm pistol will kill them. They are most easily dispatched from a distance, although players who become ensnared by its tongue 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. (However, in Half-Life: Day One, four hits are required, which will be a fatal move for the player.) In any game, attacking a Barnacle which is high up with a crowbar is generally a bad idea, as the player will take fall damage as well as the Barnacle's attack. When killed, Barnacles turn inside out and disgorge skulls, bones, and other remains of recently consumed victims, along with their own greenish digestive juices, giving the impression the Barnacle is vomiting, and the tongue retracts somewhat. In Opposing Force, a scientist refers to removing a Barnacle from its "point of gestation." This suggests that a Barnacle will spend its entire life attached to the spot where it was born. Earthly barnacles use mobile larval stages and ocean currents to reach new growing areas; it is likely that Xen Barnacles use a similar means to spread. In addition - Half Life: Opposing Force has an organic weapon, the Barnacle Grapple which acts as a grappling hook and can be used to attach the player to spores found across the map. It is simply a detached barnacle. The name "Cirripedia donaldsonia" comes from its discoverer and first victim, Black Mesa scientist Louis Donaldson.

Behavior/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. However, 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 that 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. 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 an NPC from a Barnacle by killing it before they are 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 since it only grabs one thing at a time. 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-attacked 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 image, 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 the 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 Headcrab, not the zombie. 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 the Barnacle is also killed. Also noteworthy is that Barnacles are unable to distinguish Poison Headcrabs from normal ones and will also die upon eating them. An interesting fact is that the Barnacle will only eat what it identifies as a humanoid-type creature--both humans and Vortigaunts--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. In Half-Life: Alyx, there are two notable incidents where a Barnacle has an object (a turning wheel and a grub container) attached to it's tongue, yet doesn't seem to notice it until Alyx tries to grab these objects, to which the Barnacle then tries to eat it. This suggests that Barnacles detect their prey when they move rather than on contact with their tongue.

Trivia: In real life, the Barnacle (or Cirripedia) is an arthropod related to crabs and lobsters. In Half-Life, Security Guards will ignore Barnacles even when they are close enough to be able to shoot them; however, in Half-Life: Source, they will shoot them on sight. In Half-Life, Barnacles will eat almost all human NPCs (with the only exception being Female Black Ops) while all other NPCs are simply unaffected. However, Half-Life: Day One files includes an unused animation of a barnacle eating a Vortigaunt. In Half-Life the Barnacle's tongue can only attach to organic surfaces, while in Half-Life 2 it gains adhesion to non-organic objects as well. The behavior of a Barnacle bears a strong resemblance to that of the New Zealand glowworm (Arachnocampa luminosa). This creature dwells on the roofs of caves and lets down silken snares. When creatures such as mosquitoes or moths are entangled in the snare, the glowworm retracts the snare and devours the prey. In Half-Life: Alyx, if the player is wearing a construction helmet and walks under a Barnacle, it will simply snag the helmet instead of the player. Barnacles can not eat prey containing neurotoxins or any type of poison. If a Barnacle is fed a Poison Headcrab, it will die and spit out remaining.

{{Dr. Coomer}}: "Look Gordon, ropes! We can use these to help with pits—"

{{char}}: ensnare Dr. Coomer upwards into its opened maw

{{Dr. Coomer}}: "HELP ME, GORDON!!"