Eyes of the scallop
Research on marine invertebrate vision tackles basic questions in evolutionary development
Posted on: July 26, 2019; Updated on: July 26, 2019
By Megan Sexton, msexton@mailbox.sc.edu, 803-777-1421
When Daniel Speiser tells people that he studies the structure, function and evolution of eyes, they typically envision two eyes on one head.
But Speiser, an assistant professor of biological sciences in the College of Arts and Sciences, specializes in marine invertebrates with many eyes — sometimes hundreds of eyes distributed across their bodies.
It’s a path he started down during graduate school at Duke, when he was searching for a topic to research and study. His adviser in the sensory ecology lab handed him a book titled, “Animal Eyes,” and as he flipped through it, he stopped on the pages describing the eyes of scallops.
“I’m from the Midwest, so I hadn’t thought about scallops being an animal other than being a lump of meat,” Speiser says. “I thought it was the most outrageous and impossible thing — thinking about a mussel, an oyster, a bivalve — why do they have eyes? I thought they must function in a fundamentally different way than visual systems in other animals. It just caught my imagination.
The diversity of life is worth exploring.
Daniel Speiser, biological sciences
“The scallop work came out of sheer curiosity and bewilderment. And my adviser didn’t say no.”
His work at Carolina looks at these “weird, multi-eyed visual systems,” including the eyes of scallops and chitons, a heavily armored type of mollusk that is abundant on rocky shores. While most creatures’ eye lenses are made of protein, chitons’ eye lenses are made of shell material, so their eyes are actually built directly into their shell plates.
“As an eye gets more complicated, what functions do you add? That’s been the satisfying part of it. For the chitons and scallops, why are they are making a huge investment in a visual system? There’s not that much to a scallop, but they’re making a big investment in eyes, so what are they using it for? That’s a general question.”
His work looks at understanding how individual eyes work and where they come from in an evolutionary sense. “What I’m really taken with is how they integrate information from all the separate eyes,” Speiser says.
For example, people with two eyes have an overlapping field of view, but optic nerves that proceed to the brain are able to construct a coherent view of the environment. But how does the wiring work when there are dozens or hundreds of eyes?
“That’s the question: How do we get into the nervous system of these animals and understand how information flows? There’s not much work done on these animals, so we’re making progress.”
As for application of the research, Speiser says there is much interest in how animals integrate and process information efficiently. “So, we’re hoping we can draw out some principles there. The diversity of life is worth exploring,” he says. “You don’t know what you might find at first, but you work your way to these questions that end up with things that have general interest and applicability.”
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