Polarization vision can improve object detection in turbid waters by cuttlefish
Résumé
The use of polarization vision to improve visibility through turbid water has been proposed by different researchers, but has rarely been tested behaviorally. Cephalopods perceive the polarization of light but the function of this sensitivity is not fully understood yet. In this two-phase study, we examined the ability of cuttlefish to detect an artificial stimulus through water of different turbidity, with or without polarization information. We tested responses of Sepia prashadi and Sepia pharaonis to computer generated looming stimuli, presented through different levels of water turbidity. Stimuli were presented with a modified LCD monitor delivering polarized pattern that could not be detected without a polarization analyzer, and via a CRT monitor delivering an unpolarized, intensity contrasted image. The results showed that both cuttlefish can use their polarization vision to detect objects, such as a predator. Both species detected the pattern when it included a polarization component, through higher turbidity than when it contained only intensity information. Cuttlefish are nectobenthic organisms which probably often experience low visibility conditions. Therefore the ability to see further into turbid water and to better detect prey and predator would be beneficial for their survival.