CRONIN, TW; SHASHAR, N; CALDWELL, RL; CHEROSKE, AG; CHIOU, TH; UMBC; Interuniversity Institute of Eilat, Israel; UC Berkeley; UMBC; UMBC: Polarization Vision and its role in Underwater Signaling

There are no natural sources of polarized light of known biological significance. Nevertheless, partially linearly polarized light is abundant in natural scenes, commonly being produced by scattering or reflection. Visual pigments, the molecules in photoreceptors that initiate the process of vision, are inherently dichroic, differentially absorbing light according to its axis of polarization. Many animals have taken advantage of this property to build receptor systems capable of analyzing the polarization of incoming light. It has long been known that such polarization sensitivity (PS) is frequently associated with behavioral tasks like orientation or navigation. However, only recently have we become aware that PS can be incorporated into a higher-level visual perception akin to color vision, permitting segmentation of a viewed scene into regions that vary in their polarization. By analogy to color vision, we call this capacity polarization vision (PV). PV is apparently used for tasks like those that color vision specializes in: contrast enhancement, camouflage breaking, object recognition, and signal detection and discrimination. While color is very useful in terrestrial or shallow-water environments, it is an unreliable cue deeper in water due to the spectral modification of light as it travels through water of various depths or of varying optical quality. Here, polarization vision has special utility, and consequently has evolved in numerous marine species. In this presentation, I will discuss the most recent findings concerning polarization vision and its significance to the biology of a diversity of marine animals.