While mantis shrimp are best known for their incredibly powerful punches, new research from scientists at the University of Bristol shows the small crustaceans have some of the most unique eyes on Earth. The animals’ eyes — which sit on the end of long stalks — rotate independently in all directions and always know which way is up. That includes even if the shrimp are spun completely around.
The organs are special because they have three “pseudo-pupils” all stacked on top of each other. In addition, each eye has independent depth perception and they are able to see both ultraviolet and infrared wavelengths. Mammals have three type of photoreceptor cells. Mantis shrimp have 12.
Their color vision is especially interesting because the crustaceans analyze their environment in the same way a scanner captures a photograph. That is to say, they spot a band of color, move their pupil through it, and then repeat that process over and over until the image comes into view.
In the new study, researchers took a close look at the eyes to see how the shrimp maintain their focus in a rotational world. To do that, the team built a testing tank and filled it with high-speed cameras to capture eye movements. They then placed a drum around the aquarium — to simulate a tunnel — and spun it like a wheel.
While researchers assumed the shrimp would spin their eyes to keep a stable view of the drum, they did not. In fact, in some cases their eyes went in the exact opposite direction. As a result, eyeball orientation appears to have little bearing on the way the animals view the world.
“[R]olling has absolutely no effect on their perception of space at all: up is still up, even when their eyes have rolled completely sideways,” said lead author Ilse Daly, a researcher from the University of Bristol, according to Inquisitir.
Though these findings are interesting, researchers are not sure why mantis shrimp view the world in that way. However, they postulate that roving eyes might work best when the animals remain stationary.
“It’s possible the mantis shrimps just don’t have a real sense of how the world is laid out,” he said, The Washington Post, University of Maryland Baltimore County biologist Thomas Cronin, who has studied the vision systems of mantis shrimp since 1983 and was not involved with this research.
The research was published in the journal Proceedings of the Royal Society B.