An Australian mantis shrimp can see six different types of polarisation, according to researchers, adding to the crustacean’s already impressive list of ocular abilities.

Gonodactylus smithii was already known to see things in the ultraviolet and infrared. Now Sonja Kleinlogel and Andrew White, of the Max Planck Institute for Biophysics in Frankfurt and the University of Queensland respectively, have shown that the shrimp can detect four linear and two circular polarisations (press release, research paper in PLOS One).

Basically they have some ability to detect the direction in which light waves are oscillating. See here for an explanation of linear and circular polarisation.

“The mantis shrimp is a delightfully weird beastie,” says White. “They’re multi-coloured, their genus and species names mean ‘mouth-feet’ and ‘genital-fingers’; they can move each eye independently, they see the world in 11 or 12 primary colours as opposed to our humble three, and now we find that this species can see a world invisible to the rest of us.”

The details of how they did this research are not carried in the press coverage. It’s a bit gory, so if you winced at Un Chien Andalou stop reading now…

Animals were anaesthetized by cooling before the eyes were removed and the animal euthanized by decapitation. … The amputated eye was mounted on a plastic rod with the lateral mid-band region oriented horizontally and immersed in oxygenated stomatopod saline.

Then microelectrodes were “lowered vertically into the retina through a corneal hole cut with a razorblade”. These bionic eyes were then tested with a light source and various filters to establish the polarisation detecting abilities.

I warned you to stop reading…

Detecting polarised light may also help them find dinner as some of their prey are transparent. They’d be hard to see in the water, says White, but they are full of polarising sugars. “I suspect they light up like Christmas trees as far as these shrimp are concerned,” he says.

Freaky Shrimp Species Has Singular Sight – Discover Magazine

Shrimp can see beyond the rainbow – Reuters

Shrimp with super-vision revealed – PA

Image: Gonodactylus smithii / Roy Caldwell