Meeting Abstract
Snapping shrimp (Decapoda: Alpheidae) produce shock waves with their snapping claws and they use these shock waves to stun or kill predators, prey, and competitors. Snapping shrimp also have an extension of their carapace—termed the orbital hood—that may protect their heads against these shock waves. The presence of armor over their eyes has led to the hypothesis that snapping shrimp have impaired visual abilities. We tested this hypothesis and found that the snapping shrimp Alpheus heterochaelis can see through their highly transparent orbital hood. To do so, we conducted behavioral experiments employing the optomotor responses of A. heterochaelis and showed that these snapping shrimp have an angular resolution of ~ 8 degrees. After demonstrating that A. heterochaelis has a functional visual system, we next asked if the presence of the orbital hood affects its visual abilities. The transparency of the orbital hood suggests it does not help or hinder vision in A. heterochaelis, but its high refractive index (n = 1.525) suggests it may influence vision in this species. To assess the impact of the orbital hood on vision in A. heterochaelis, we performed optomotor trials on a group of shrimp with intact orbital hoods and a second group of shrimp from which we removed the orbital hoods. Our stimuli consisted of alternating black and white vertical bars with angular widths of 2, 4, 10, and 20 degrees, as well as a control stimulus that was a uniform grey. From these trials, we found that snapping shrimp demonstrate spatial vision whether their hoods are present or absent. Further, preliminary results indicate shrimp with intact hoods may have more acute vision than those without hoods, and that orbital hoods may contribute to vision in snapping shrimp.
