Visual Physiology of the Antarctic AmphipodAbyssorchomene plebs

Although the visual systems of animals living in the cold, dark water of the deep sea have been investi- gated for some time, little is known about vision in animals inhabiting polar oceans, where temperatures are even colder and irradiance fluctuates dramatically with ice cover and season. Physiology of the compound eye of the amphipod Abyssorchomene plebs (Gammaridea: Lysianassoidea), a common Antarctic benthic scavenger, was studied electro- physiologically by electroretinography. A. plebs has a monochromatic visual system with a spectral sensitivity maximum at 487 nm, and higher sensitivity at ultraviolet wavelengths than predicted by a visual pigment template. While irradiance sensitivity determined from V/log I curves is comparable to that of mesopelagic crustaceans, temporal resolution calculated from response waveform dynamics and as determined by critical flicker fusion frequency sug- gest that the A. plebs eye is slower than that of crustaceans from the deep sea. A. plebs photoreceptors are physiologi- cally adapted for a slow lifestyle in a low-light environment, where maximizing photon capture occurs at the expense of detecting fast events in the visual scene.