Some people are deathly afraid of all bugs that exist on earth while others seem at ease in the presence of even the most intimidating looking creepy-crawlies. But it is hard to imagine anyone getting cozy with an arachnid that measures nearly six feet in length. Of course, it is hard to imagine a creature that does not exist, but the now extinct Pentecopterus decorahensis arthropod species did, in fact, grow to be nearly six feet long before eventually emerging from their ocean habitat to become the first terrestrial arthropods in existence. This species is the oldest known ancestor of modern day scorpions, and they were the first predatory animals to exist. In addition to looking just like a scorpion, only huge, the Pentecopterus decorahensis species possessed a spiked tail and had sharp claw-like features protruding from its head. While modern arachnids, like scorpions and spiders, do not possess these particular otherworldly features, there is a one remarkable physical feature that some modern scorpion species do possess–12 separate eyes.

All scorpion species are nocturnal, so visual perception is not the most important sensory ability that scorpions rely on in order to hunt and survive. This is why some scorpion species, especially cave-dwelling species, have not developed eyesight as an adaptive feature. Strangely, however, there exists some scorpion species that possess 12 eyes that are located in various bodily regions. In fact, some researchers even believe that a scorpion specimen is one big eye.

According to biologist Douglas Gaffin of the University of Oklahoma, the entire exoskeleton of a scorpion may actually be one giant photoreceptor that converts ultraviolet sunlight and moonlight into colors that are visible to scorpions. This would explain why scorpions glow under ultraviolet light, which is a feature that has been traced back to the earliest sea scorpion giant. Scorpions may have adapted to perceive light wavelengths that cannot be seen by most other animals, allowing them the advantage of finding shelter and prey during the dark of night.

Do you think that bioluminescence and visual perception are linked in other glowing arthropods?