Meeting Abstract
The evolution of eye size has been studied across multiple taxa. In general, predators evolved larger eye size per body mass as an adaptation for locating their prey and some prey evolved large eyes, increasing their visual acuity as they flee from their predators. Most research on invertebrate eye size have focused on species with high visual acuity. Consequently, little attention has been given to the evolution of eye size in scorpions, which have limited vision. Scorpions are nocturnal predators that rely primarily on specialized setae to detect substrate and air vibrations of their prey. However, the persistence of the eyes in most scorpion species suggests the eyes are functional, albeit not for prey capture. Research has shown the eyes of scorpions are sensitive to changes in ambient light and may assist with celestial navigation and circadian rhythms. Although many scorpions are desert inhabitants, others occupy a variety of habitats, including environments with significant canopy cover. Therefore, we wanted to test if there were eye morphology adaptations to these different environments. This research tested the relative size of the median eyes in two scorpion species that inhabit different environments, with different levels of ambient light available. It was predicted that scorpions in a forested habitat evolved larger eyes in the lower light environment. The diameter of the eye and the carapace length of fifty-six specimens total, were measured. Controlling for carapace length (measure of body size), eye size was larger in the scorpion species that occupies a forested environment compared to the desert species. Our findings suggest that it may be advantageous to have larger eyes if in an environment with significant canopy cover.
