The eyes of a cuttlefish are very different to humans, but scientists have discovered we have one spec-tacular thing in common - we both see objects in 3D. But the mechanism behind that stereopsis is probably very different.
"This study takes us a step further toward understanding how different nervous systems have evolved to tackle the same problem", Rachael Feord, a graduate student at Oxford University, the research paper's first author, said in the statement.
In the study, the team trained cuttlefish to wear 3D glasses and strike at offset images of two walking shrimp.
Previously, they showed that bumps that dot the skin of cephalopods, known as papillae, are used for sensory perception.
The researchers proceeded to play a video of shrimp, which is one of cuttlefishes' favorite prey. The only problem is majority probably aren't waterproof so even cuttlefish wouldn't want them. This means their brains allow them to discern distances. And although their eyes are normally positioned to the side of the head, rather than forward-facing, they too are capable of stereopsis because of their ability to rotate their eyes to a forward-facing position. "But if you flip the images and make the shrimp look like they are behind the screen, they will swim directly in it".
Trevor Wardill, assistant professor at the department of ecology, evolution and behaviour at the University of Minnesota, said: "How the cuttlefish reacted to the disparities clearly establishes that cuttlefish use stereopsis when hunting".
"When only one eye could see the shrimp, meaning stereopsis was not possible, the animals took longer to position themselves correctly".
When you're watching a 3D movie, your brain is combining the offset images, as seen differently by your left and right eyes, to make you think that flat images have depth, and some are closer than others. Scientists in the United Kingdom have shown that praying mantises also have binocular depth perception (a discovery also made with tiny 3D glasses). They thought there was something unique about the praying mantis.
Cuttlefish were outfitted with special glasses in a tank at the Marine Biological Laboratory in Woods Hole, then shown a 3D movie of tasty shrimp on an underwater screen: They lashed out at their prey as if they had been fooled by the images, indicating that they have depth perception, researchers said.
A study published Wednesday in the journal Science Advances suggests that, contrary to what scientists believed in the past, cuttlefish can see in three dimensions and use their brains to perceive depth.
According to Wardill and colleagues, cuttlefish compute distance using information coming from both eyes at once and likely use a different "algorithm" than humans to process the resulting images in their heads.
The next step in the research is to investigate cuttlefish brain circuits to try and figure out exactly how the stereopsis computation works.
"Creatures such as cuttlefish or mantis may seem extravagant, but understanding them will help us find varieties of artificial vision that are more appropriate for different situations, for example, for a flying drone in front of a robot vacuum cleaner or a security camera", said the professor at the University of Newcastle.