Vision in the snapping shrimp Alpheus heterochaelis.

Snapping shrimp engage in heterospecific behavioral associations in which their partners, such as goby fish, help them avoid predators. It has been argued that snapping shrimp engage in these partnerships because their vision is impaired by their orbital hood, an extension of their carapace that covers their eyes. To examine this idea, we assessed the visual abilities of snapping shrimp. We found the big claw snapping shrimp, Alpheus heterochaelis, has spatial vision provided by compound eyes with reflecting superposition optics. These eyes view the world through an orbital hood that is 80-90% as transparent as seawater across visible wavelengths (400-700 nm). Through electroretinography and microspectrophotometry, we found the eyes of A. heterochaelis have a temporal sampling rate of >40 Hz and have at least two spectral classes of photoreceptors (λmax=500 and 519 nm). From the results of optomotor behavioral experiments, we estimate the eyes of A. heterochaelis provide spatial vision with an angular resolution of ∼8 deg. We conclude that snapping shrimp have competent visual systems, suggesting the function and evolution of their behavioral associations should be re-assessed and that these animals may communicate visually with conspecifics and heterospecific partners.