Vision researchers at the University of Minnesota recently put a lens on cuttlefish.
In an effort to improve their understanding of depth perception, a team led by Assistant Professor Trevor Wardill found a way to put 3-D glasses on the small, squid-like creatures.
Designing the glasses was one challenge; getting the cuttlefish to wear them was even trickier.
“I designed how to train the cuttlefish to wear the glasses,” Wardill said.
Cuttlefish were chosen because, like humans, they perceive depth with both eyes, a process called stereopsis.
“These animals were good to use because of the way their eyes function,” Wardill said. “They have a similar type of eyes to ours, what we call the camera type eye. They also rotate their eyes when they’re about to strike, so again, similar to us.”
The research team built the 3-D glasses and an underwater theater with sensors that simulate shrimp — a favorite cuttlefish morsel — to see how cuttlefish determine the best distance to strike at their prey.
They found that cuttlefish not only have depth perception equal to that of humans, but senses that are even better.
While scientists were familiar with the depth perception skills of cuttlefish, this project discovered that the animals were even more skilled than previously thought.
“It has an ability to determine depth even when the intensity of the left and the right eye differ quite a lot,” Wardill said. “That means that they can deal with collateral or changes in the environment, but still not be affected by those distractions.”
Depth perception in humans is not always that successful.
Much of the research was conducted at the U last summer, and the animals were trained to wear the glasses at the Marine Biological Laboratory in Woods Hole, Mass. The team’s findings were published Wednesday in the scientific journal Science Advances.
Designing effective 3-D glasses for a small marine animal was a challenge in itself.
“They’re made from fairly thin plastic; they don’t weigh very much. But that means they can also bend, so we had to put different shapes and kinks in them to sort of strengthen them so that they would hold up to the animal swimming around,” Wardill said.
The glasses went through several versions before the researchers landed on the perfect design, which they attached with Velcro.
While Wardill admits the image of cuttlefish doing laps around the tank wearing colorful 3-D glasses is amusing, the work had its frustrations.
“Cuttlefish, when you move them from one tank to another tank, if you’re not extremely careful, they will [expel] ink and make the water very cloudy and black,” Wardill said. “Meaning that you can’t really do any video experiments.”
The team had to learn quickly how to move the cuttlefish around very gently. Not to mention keeping the glasses on the creatures.
“Quite a few cuttlefish would take the glasses off … just sort of reach up and pull them off,” Wardill said. “It can be very frustrating.”