first of all, aliens do NOT explode in space. They can withstand pretty much all conditions & temperatures. The vacuum of space is no different. For reference, in Alien when Ripley fires the harpoon into the drone while it is holding onto the door & it gets blown out into space, it doesnot explode, & in fact, it tries to reenter the ship through the "exh" (for lack of a better word), so aliens can withstand the vacuum of space.
Second of all, the tubes on the drones/warriors backs are most likely for creating & storing the resin that the walls of the hive are made from. The resin is probably either ejcted from pores in the tubes themselves, or the resin p through the aliens body first & is then ejected from the mouth. Only drones/warriors can produce the resin, meaning the "runner" would not need the tubes. They are not for breathing either way because aliens don't need oxygen to survive