I didn't stop to think but are Xenomorph actually resistant to acid corrosion? After finishing this I remembered that scene from AvP where they spread acid on the queen to free her and she was hurt.
In this one I was worried both of their bodies being gray, plus the pose would make it a bit harder to tell them apart.
But I am happy that wasn't the case, at least in my eyes and monitor.
My knowledge of Halo grew 1 point as I researched the wiki to figure out what the dialogue should be in this one.
I really gotta play the Bungie trilogy..