Xenomorph spikes

The tubes on the original adult  xeno are for breathing, I've read that from a few different sources over the years

We would have to wonder how does the Chest Buster Breath, and Deacon if that was the case...

Not saying its not the case, we have heard many theories over the years which include this is where they secret the Material to Make the Hives and Cocoon Hosts...

I really do hope we get a explanation for their purpose down the line, in the mean time its fun to speculate and indeed the closest we have to these as far as Organisms on Earth would point to some kind of Respiratory aid.  For example like  Spiracles

The tubes - design wise - are to break up the human shape to make it look less like a man in a suit.  Giger didn't like them, hence the absence from the Alien3 designs.

As for what they're for - they've never been given a defined purpose.  The 'breathing' thing is a popular myth.

I've been wondering this for years(nearly 27 lol)I don't know their exact purpose.

I hadn't heard the breathing theory, the only theory id heard of was they use them to excrete the resin to construct the hive and cocoons, which makes sense. when we see the first signs of a xeno it is usually a gooey substance on the floor that most dip their fingers in. now, im assuming this is drool. if the xeno used the drool from their mouth as the substance for the hive etc, it would stand to reason it wouldn't be gooey when the humans come across it, as the substance would need to harden pretty quickly to cocoon a human.

Resin spinarets is another popular but ultimately unsubstantiated theory (one that I quite like until you hit a wall called Alien 3)..

Indeed S.M. Could they possibly be related to the creation of a hive and cocooning?

think that's the theory I mentioned

Oh,sorry S.M. I should have read a little closer 

I believe one of the unproduced alien3 scripts depicted this theory and if in not mistaken, it may have appeared in comics aswell?

We need a movie with a Xeno autopsy ;)

"As for what they're for - they've never been given a defined purpose.  The 'breathing' thing is a popular myth."

Indeed i think as you mentioned to both those theories.. they do conflict as far as Alien 3 goes..  which leads to two problems.

1) If they are for breathing then why does the Alien 3 Organism lack them.... why should the Runner be much different Biologically?

The only conclusion would be some how the Runner having Face Hugged its Victim on a World/Prison that has a inhabitable atmosphere does not need those breathing Tubes.

2) The Resin idea... again we have to wonder what is the purpose of the Runner, i assume the Franchise was all about showing these Organisms had a prime reason for its survival and this was procreation....   we have to ask what purpose does a Drone from Alien have regarding how it would connect to the differences in Aliens...  surely it is some kind of Scout but what the point if there is nothing to Scout back to... its not going to get back to other Eggs and say "right guys i found a perfect set of Hosts to build a colony"

It had to play a more direct role, and purpose for why it had those Pipes/Spiracles and so we again have to ask why does the Alien 3 Runner not have them...... does this mean the Runner in no way can set up a Hive, Create those Resin like Structures and Cocoons? or even Egg Morph?

We have to REMEMBER the Queen also lacks any Pipes/Spiracles so a logical explanation is they are aquired by a Human Host... but then we have to wonder where did a Queen come from? 

Because Again Alien 3 shows us a Queen Embryo Gestates in a Human Host (or other Host) If it was not for Alien 3 then we could safely speculate that a Queen is created by some other means that is not via Face Hugger or indeed not from the Eggs on the Derelict... but alas....

I Wander if the 10 page Rule book on the Xenomorph etc, will explain the use of those Pipes/Spiracles and another thing to remember is what if Fox/Ridley decide that Blomkamps idea to remake a alternative sequel to Aliens is a good idea?

They could make another movie that replaces Alien 3 and Alien R to get away from those inconsistencies or explain them...  but this would be speculation at the moment.

But i do think a Alien 5 will happen 100% for sure, i cant say it will be Blomkamps but it could use some of his ideas, and certainly we would see a movie that in the Time-frame is set after Aliens.

@ S.M., Giger had nothing to do with the design for the Alien in Alien 3, as ADI developed their designs for the Bambi and Runner Alien without his input, even going so far to ignore any and all of Giger's suggestions. Though ironically Giger did create separately a similar design with the Cougar Alien. Also as depicted in Necronomicon IV, the dorsal tubes were Giger's idea...

However, you do bring up a good point that Alien 3 does upset the two leading theories for the Aliens 4 dorsal tubes. Personally, I have always believed that the Aliens breathe and secrete their resin from their mouths.

A possible use for the tubes could be temperature control, with most breeds needing to vent body heat due to the lack of pores from possessing and exoskeleton. With the Runner Alien being much more fleshier than its precursors, it may have genetically acquired pores, bypassing the need for the dorsal tubes.

But remember that most Alien breeds also possess a fifth dorsal appendage, located just behind the head on the creatures spine, above the dorsal tubes. This dorsal "fin" could be used for anything.

the bio mechanical structure of the sprinter should be the same regardless of host no? whether its bipedal or a quadruped and over all shape of the xeno r traits taken from the host but id assume the over all organic/ bio mechanical structure of the creature should remain the same as the face hugger is the same type that spawned the bio mechanical xeno in aliens

The tubes mean nothing.  Just a drawing by Giger, pre-Alien. With the greatest respect some people think too much.

As for the Deacon - although I need to see the movie again (although I have seen it so many times that I SHOULD know this lol) - I thought it used it's pointed head to tear through the Engineer, and not spikes on its back which I don't recall it having.

Yes you are correct, The Deacon tore out of  victim body with pointy head and has no back venting. If they aren't for respiration I like the idea above that they are for temp control due to the exo skeleton , that makes sense as well as the possibility of respiration, biologically speaking

Big Dave! The Queen have tubes/spikes, they are just different. 

             "Bees have hives, man " 

The Chestburster breathes through little 'gills', which you can clearly see in action as it looks around at the crew.

The multifunction tubes and spikes could also be for balance, the MORB's elongated cranium would cause difficulty in remaining upright were it not for the tubes, plus the tail?

I always thought they were possibly a throw back to earlier DNA - in that perhaps a creature used along the way had defensive spikes on its back that became what we see in ALIEN.

@ Phallic Jaw Yes, you're right but the fun is in speculating, surely? :) 

I find it interesting now because to make this whole thing work and back into ALIEN, little details like this are probably going to need to be explained; especially if we see David create or recreate the Xeno (God, I hope it's the latter).

Giger designed the tubes AND neck spike. They belong there. It IS part of the original Xeno. What they're for? Who knows?

ANY Alien movie depicting a "classic" Xeno without said tubes and spike is an abomination and one that I do not consider "canon", and neither would RS or Giger, the HORRIFIC CGI apparently birthed by a kindergartner graphic design student in Alien 3 notwithstanding.