Alright, here comes the Barnacle Biology Manifesto. As a biologist, it’s pretty clear to me that almost nobody in this argument knows what they’re talking about, and while I realize that nobody’s going to care that I’m (and that at least one person is going to call me some variation of a “douchebag” for) writing this, it should at least shed some light on this whole stupid thing.
First of all, we have to assume that the nature of matter in the Xen dimension and our dimension are identical. That is, matter is still composed of atoms, and we still have the same set of elements as defined in the periodic table. Proof: If the nature of matter wasn’t the same, there would be no way for creatures from Xen to exist on Earth and vice-versa. Only one nature of matter is known to man, and the only other nature of matter theorized is antimatter. If the Xen dimension were made up of antimatter, then anything travelling between the dimensions would instantly annihilate upon entering the other dimension. If Xen were to be composed of some unkown form of matter, then that matter would not be able to interact with Earth-matter in a way that could sustain life.
Secondly, this:
This argument has a gaping hole in it. Xen is a borderworld dimension, crammed between two other universes… for all we know, it could be bathed in all kinds of bizarre radiation and as-of-yet unidentified particles (Dr. Breen even lends credibility to this idea during his taunting as his teleport ascends at the end of Half-Life 2). However, even if there is “feng-shui energy” on Xen that might sustain its native organisms, there is no such energy on Earth, the consequence being that the Barnacle would not be able to survive at all on Earth in the absence of said energy. The fact that Earth organisms can survive comfortably on Xen also suggests that no such energy is present, and that the organisms there rely on more conventional energy sources. (Another supporting point for this argument: Houndeyes and Bullsquids can clearly be seen breathing. If life on Xen is descended from a single common ancestor as it is believed to be on Earth [which is an extremely reasonable assumption], than it follows that barnacles also respire.)
One could conceivably argue that the Resonance Cascade might be bathing the Earth in the aforementioned energy and allowing the Barnacle to survive, but this is also easily debunked when you consider that the barnacle remains on Earth during the time at which Half-Life 2 took place. The resonance cascade is clearly over at this point, and contact with the Xen dimension has been cut off. Unless, through some freak coincidence, the Combine’s native universe is rife with the same energy as Xen, it’s easily concluded that the energy does not exist.
Third: Xen organisms and Earth organisms both breathe oxygen. That is, in the process of cellular respiration, they liberate energy-rich electrons from the chemical bonds of their fuel sources, extract that energy via an electron transport chain of some kind, and use oxygen as the final electron acceptor for the then-depleted electrons. Proof: This is where it becomes important that the state of matter is the same on both Xen and Earth. Take the fact that Xen organisms can be seen breathing, along with the previously stated fact that Xen and Earth organisms can breathe in both Xen and Earth environments. Also applicable is the fact that oxygen - due to its unique chemical composition - is the ultimate electron acceptor. The only reason that life was able to evolve into the complex multicellular structures that we see on Earth today is that oxygen provided by early plants proved an invaluable asset to respiration. Take the fact that anaerobic respiration - respiration in the absence of oxygen, as is performed by many bacteria, yeast, and other microorganisms - nets a gain of two ATP (Adenosine Tri-Phosphate, the biological “energy currency”), while aerobic respiration - respiration that utilizes oxygen - nets a gain of thirty-eight ATP (per cycle, in both cases).
Fourth: Liberating oxygen from a liquid atmosphere requires a completely different physiological structure than liberating oxygen from a gaseous atmosphere. Proof: If I need to prove this to you, then you have no business sharing this planet with me. If you don’t believe it, try sticking your head in a bucket of water and seeing how easy it is to breathe in there. Or, grab your goldfish out of its bowl and lay it on the tabletop, and time how long it takes the thrashing to cease.
The only variable that remains:
First things first: Earth barnacles can’t technically breathe both above and below water. When the tide recedes, leaving the barnacle exposed, it clamps its shell shut, sealing a few drops worth of water inside with the body of the organism itself. Because the barnacle is such a tiny organism, the meager oxygen content of this water is enough to sustain it until the tide rises again. Xen barnacles are many hundreds of times larger than Earth barnacles, so even if they had some sort of mechanism to accomplish a similar feat (which they don’t, at least visibly), the Xen barnacle would require thousands of times as much oxygen to sustain itself for a similar period of time. Its “shell” would have to be enormous. Additionally, there is a huge body of evidence (as has been referenced in numerous arguments before mine) showing that the barnacle lives exclusively above water. Not once has it been observed in an aquatic environment. And while “the absence of proof is not the proof of absence,” no credible scientist can in good faith simply disregard such a large chunk of data.
Just to be thorough, I’ll go even further: Xen barnacles, like Earth barnacles, clearly rely on touch as their primary sensory mechanism. (Proof: It’s obvious, you cretin.) In an aquatic environment, a sensory organ as huge as the Xen barnacle’s tongue would drift in any current and light on all kinds of inanimate objects, like rocks, which it would then spend unnecessary energy attempting to ingest. (Barnacles cannot distinguish between potential prey and inanimate objects, the proof being that they attempt to gobble up any old thing that you feed them in HL2.) The barnacle specializes in lying in wait for prey: ambient underwater currents would deprive it of this technique. And this doesn’t even touch on the numerous other complications presented by an underwater environment, such as increased density and pressure (which would require a stronger skeleton) and osmotic pressure (the tendency of water to diffuse across membranes to areas with higher solute concentration [layman’s terms: water flows to where there’s more stuff, like a cell, for example; you may notice it after you go swimming for an hour or so and come out of the water with pruny fingers and toes]), which eventually causes cells to burst, and is a huge problem for any aquatic organism.
CONCLUSION: XEN BARNACLES LIVE EXCLUSIVELY IN NON-AQUATIC ENVIRONMENTS. And even if, as has been suggested, they somehow adapted or were modified to live in underwater environments, that adaptation, by the very biological definition of “adaptation,” would make them a new species.
One final point: EVERYTHING that I have used in this argument - except possibly the finer nuances of (Earth) barnacle biology, which I happened to learn in a high school biology class several years ago - are COMMON KNOWLEDGE in my field of expertise. I DID NOT copy-paste any of this information. Now STOP talking out of your asses about things you don’t understand; it’s sickening.
-> :hmph:
Now how fucking win is that?!