You may not have known about the spiders that thrive in arctic environments, but they do exist. Actually, the spider-like creatures that have been spotted in arctic waters are not spiders, rather they are classified as a type of arthropod know as pycnogonids. These arctic bugs can grow to astonishing proportions with body lengths reaching a full twenty inches across. However, researchers are still unsure as to why these arctic bugs are so much larger than their spider relatives.
One theory says that these huge arctic bugs may have evolved from deep sea spider-like creatures, which are known to be as large in size as the arctic bugs spotted near the surface of arctic waters. Now, after having studied the arctic environment more closely, researchers seem certain that the excess oxygen that forms in response to extremely cold water temperatures is what allows these arctic bugs to become so large in size. Bugs located elsewhere on this planet have not had to adapt to the same high oxygen levels. Higher oxygen levels in the arctic waters can only be tolerated by organisms with bodies large enough to process the excess oxygen present in their environment.
Since higher oxygen levels result in larger bodied arthropods, then would it be sensible to assume that there exists extra small arthropods in low oxygen environments, such as mountain tops?