16. Japanese Spider Crab
The Japanese spider crab boasts the largest leg span of any arthropod, reaching up to 12 feet, which can appear quite intimidating. Yet, this giant of the ocean leads a peaceful life as a scavenger, feeding on dead animals and plant material along the seafloor. Endemic to the waters around Japan, these crabs play an essential role in marine ecosystems, cleaning up detritus and maintaining environmental balance.