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What the Cuttlefish Saw: 3D Hunting and the Structure of the Brain

What the Cuttlefish Saw: 3D Hunting and the Structure of the Brain

cuttlefish hunting

If the octopus is the mastermind of the sea, then I consider the cuttlefish its tough, canny cousin — a cephalopod enforcer with a literal backbone (not really: it’s an internal shell), a Joe “Pesce,”  if you will.
 
Okay, okay, I’ll stop… But a team of scientists from the University of Cambridge and the University of Minnesota won’t: won’t stop trying to understand the cuttlefish predation process using unusual and hilarious means, that is! In an experiment conducted at the Woods Hole Oceanographic Institute, the team outfitted cuttlefish with 3D glasses — the classic, monster-movie, red-and-blue ones — in an effort to find out how they hunt their especially skittish aquatic prey. Turns out, it’s a delicate proposition: cuttlefish use their long dual feeding tentacles to snag dinner, and they have to be just the right distance. If not, they risk scaring the doomed shrimp or crab away, or even missing it entirely. Humans use stereopsis, or binocular, vision as the basis of our depth perception — but do cuttlefish?
 
“To test how the cuttlefish brain computes distance to an object, the team trained cuttlefish to wear 3D glasses and strike at images of two walking shrimp, each a different color displayed on a computer screen […]

The images were offset, allowing for the researchers to determine if the cuttlefish were comparing images between the left and the right eyes to gather information about distance to their prey. […] Depending on the image offset, the cuttlefish would perceive the shrimp to be either in front of or behind the screen. The cuttlefish predictably struck too close to or too far from the screen, according to the offset.
 
‘How the cuttlefish reacted to the disparities clearly establishes that cuttlefish use stereopsis when hunting,’ said Trevor Wardill, assistant professor at the Department of Ecology, Evolution and Behavior in the College of Biological Sciences. ‘When only one eye could see the shrimp, meaning stereopsis was not possible, the animals took longer to position themselves correctly. When both eyes could see the shrimp, meaning they utilized stereopsis, it allowed cuttlefish to make faster decisions when attacking. This can make all the difference in catching a meal.’”
 
While this experiment uncovers one point where cuttlefish and human vision dovetail, that is where the similarities end. Cuttlefish process stereoscopic images differently than humans do, due to their vastly different brains. Unlike us, they don’t have an occipital lobe; that is, a part of the brain that is specifically dedicated to processing visual stimuli. That means that stereopsis in humans (and other vertebrates) and cuttlefish developed independently. The next step is for researchers to dissect cuttlefish brain circuitry, to see if they can pin this fascinating difference down!
 
It’s staggering that brains as different as humans and cuttlefish can develop the exact same skill. We humans can learn so much from the natural world — not least the fact that despite our advancements we are animals too.