The eye-rolling behavior of mantis shrimp helps them see the world, says a team of biologists led by Nicholas Roberts of the University of Bristol, UK.
Mantis shrimp — predatory, ocean-dwelling crustaceans of the order Stomatopoda — use eye rotations to improve their vision. Image credit: Michael Bok / University of Lund.
“We have known for a while that mantis shrimp see the world very differently from humans,” Dr. Roberts said.
“They can use 12 different color channels (humans use only three), and can see the polarization of light.”
“But the eye movements of mantis shrimp have always been something of a puzzle.”
According to Dr. Roberts and his colleagues, mantis shrimp are able to see the polarization of light, and by rolling their eyes they actively improve the polarization contrast of objects in their marine environment.
In order to arrive at this conclusion, the team tracked in three dimensions the eye movements of two species: the purple spot mantis shrimp (Gonodactylus smithii) and the peacock mantis shrimp (Odontodactylus scyllarus).
Rotational degrees of freedom of mantis shrimp eyes relative to the external environment. Yellow arrows – pitch (up–down); green arrows – yaw (side-to-side); red arrows – torsional (roll) rotations. Image credit: Ilse M. Daly et al.
“Mantis shrimp rotate their eyes to align particular photoreceptors relative to the angle of polarization of a linearly polarized visual stimulus, thereby maximizing the polarization contrast between an object of interest and its background,” the researchers said.
“This is the first documented example of any animal displaying dynamic polarization vision, in which the polarization information is actively maximized through rotational eye movements.”
The results were published online this week in the journal Nature Communications.
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Ilse M. Daly et al. 2016. Dynamic polarization vision in mantis shrimps. Nature Communications 7, article number: 12140; doi: 10.1038/ncomms12140
