Separate channels of polarization and brightness give crabs an advantage over predators

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Violinist crabs see the polarization of light, which allows them to better identify potential threats, such as a rival crab or predator. Researchers at the University of Bristol have begun to understand how this information is processed in the crab brain. The study, published in Progress of science has discovered today that, when detecting objects in approach, the violin crabs separate the polarization and the luminosity.

The main advantage of this method is that the separate video channels provide a greater range of information to the crab. Research also suggests that in terms of predator detection, polarization can be a more reliable source of information than brightness.

Researchers from the Ecology of Vision group of the Faculty of Biological Sciences have tested the reaction of crabs to visual stimuli presented on a special screen developed by the laboratory. By changing the polarization and brightness of the stimuli, the researchers were able to check whether certain combinations of polarization and brightness seemed to cancel each other out.

Sam Smithers, PhD A student from the Faculty of Biological Sciences and one of the authors said, "If you look over the Polaroid sunglasses, you will notice that the brightness changes when you tilt your head. is because the sky is polarized and your sunglasses allow you to see polarization differences as differences in brightness. "

"For our experiments, we checked to see if the violin crabs had the same effect, but we found that crabs detect polarization in a completely different way and polarization has no effect. effect on how crabs detect the brightness of a scene. "

The next step for the research team is to discover what happens to brightness and polarization information located deeper in the brain. This will help them understand how and when the polarization and color information provides a visual benefit to the viewer.