Why beetles don't need glasses

UC biologist will use a National Science Foundation grant to study diving beetles for insights into eye development

To understand why so many people need corrective lenses, Elke Buschbeck is looking at an unusual creature that Mother Nature endows with keen vision.

Buschbeck, a biology professor at the University of Cincinnati, is studying diving beetles, aquatic insects that begin life as world-class assassins. Buschbeck raises diving beetles in large aquaria in her biology lab where their predatory prowess is on display. Each beetle can hunt and devour as many as 800 mosquitoes during their voracious larval stage.

The National Science Foundation in August will award Buschbeck’s lab a $900,000 grant over four years to study the beetles for insights into our own visual development. The project demonstrates UC’s commitment to research as described in its strategic direction, Next Lives Here.

UC biology professor Elke Buschbeck on her work exploring insect eyes and diving beetles with student Jennifer Hassert.

UC student Jennifer Hassert inserts double-stranded RNA into a diving beetle to suppress the expression of genes relating to vision in professor Elke Buschbeck's biology lab. Photo/Ravenna Rutledge/UC Creative Services

They’re eating machines. So for them, having well-focused eyes is very important.

Elke Buschbeck, UC biology professor

UC biology professor Elke Buschbeck on her work exploring insect eyes and diving beetles.

A sunburst diving beetle in UC's biology lab. Photo/Ravenna Rutledge/UC Creative Services

More than 4 billion people around the world have visual impairments, according to the World Health Organization. In the United States alone, three in four people wear corrective lenses or have corrective surgery. Buschbeck said she hopes to use diving beetles as a model system to learn about the development of vision in invertebrates at the molecular and genetic level.

Beetle larvae have 12 eyes grouped in six pairs. Insects like dragonflies and bumblebees have large compound eyes made up of a geometric grid of as many as 30,000 tiny lenses like a disco ball. But each eye of diving beetles has a single image-forming lens like ours.

As they grow, this lens must maintain a precise distance from the retina to capture a clear image. This focal length means the difference between being nearsighted, farsighted or perfectly clear and sharp, a condition biologists called “emmetropia.”

Since diving beetles hunt by sight, keen vision is paramount, Buschbeck said.

A portrait of Jennifer Hassert.

UC student Jennifer Hassert is working with gene expression in diving beetles. Photo/Ravenna Rutledge/UC Creative Services.

“As larvae, these beetles have evolved to be predators. They’re eating machines,” she said. “So for them, having well-focused eyes is very important.”

In 2010, Buschbeck discovered that diving beetles have bifocal lenses, an oddity in the animal kingdom. Tiffany Cook, a biologist at Wayne State University who is partnering on the NSF grant, said they want to learn more about how this unusual lens forms.

“We don’t fully understand how lens development happens so we’ve been dissecting the genetic components. Perhaps that will help us design better bifocal lenses for ourselves,” Cook said.

Beetle larvae don’t have long to establish their new eye lenses with a proper focal distance once they molt and shed the old one.

“They have to reform their lens right away or they’ll starve to death or get eaten by predators,” Cook said. “Dr. Buschbeck found that the structure forms rapidly.”

UC biology professor Elke Buschbeck
with student Shubham Rathore

UC graduate student Shubham Rathore works on a gene amplifier in professor Elke Buschbeck's biology lab. Photo/Ravenna Rutledge/UC Creative Services

Cook is comparing the 12 eyes of diving beetles to the compound eyes of fruit flies. Their visual systems are not so different after all, she said.

“It was shocking that these eye types would have any relationship to the compound eye,” she said.

Buschbeck is studying the genetic mechanisms that allow beetles to maintain their vision while growing as much as 130 percent between molts, when they shed their exoskeleton, including their old eye lenses.

Likewise, beetles maintain their perfect vision regardless of environmental factors such as growing up in total darkness, which would render us virtually blind under similar circumstances, Buschbeck said.

“This is an active field of study. We know that vision itself helps to focus the eye correctly,” she said. “In invertebrates, this really hasn’t been addressed, probably because it’s not an easy thing to measure.”

UC biology professor Elke Buschbeck on her work exploring insect eyes and diving beetles

UC student Isaiah Giordullo adjusts a micro-ophthalmoscope in professor Elke Buschbeck's biology lab. The device allows biologists to study the vision of the tiniest insects. Photo/Ravenna Rutledge/UC Creative Services

The beetles are the size of an M&M and just as colorful — a warning of their toxicity to animals tempted to eat them. The larvae are tinier, still. To study eyes smaller than the dot over this i, Buschbeck and UC assistant professor Annette Stowasser, her former postdoctoral fellow, spent three years designing a custom micro-ophthalmoscope that can measure the visual acuity of beetles, spiders and flies.

The device can use a “water lens” to measure the refraction that occurs in water.

“The refractive index is higher in water than in air, so an image that would be focused in water would be unfocused in air,” she said.

The equipment can be adjusted to the half-micron, which is a necessity when trying to peer into the teeny red eyes of a fruit fly.

“It gets worse. To get the optical measurements right for a fruit fly, we have to measure one ommatidium or lens at a time,” she said.

We don’t see with our eyes. We see with our brain.

Dr. Karl Golnik, Neuro-ophthalmologist at UC's Gardner Neuroscience Institute

UC biology professor Elke Buschbeck

 with master's student Rose Conley.

UC student Rose Conley talks about her study on diving beetles in professor Elke Buschbeck's biology lab. Photo/Ravenna Rutledge/UC Creative Services

Buschbeck’s students are using diving beetles for a variety of ongoing studies. Graduate student Jennifer Hassert is studying gene expression by modifying the beetles’ RNA, the “messenger” that determines how genes are expressed. Gene expression controls things like hair color.

Natural selection likely plays a role in the beetles’ excellent vision. Diving beetles that inherit poor vision probably don’t survive long enough to pass the trait along to future offspring, Hassert said.

“If you can’t see well, you’re either going to starve or get eaten,” she said. “Since these mistakes are not found commonly in the wild, I’m inducing them in a lab and seeing if they can correct for it.”

She binds each larvae in a jellylike coat and then uses a tiny glass needle to inject double-stranded RNA in a blue dye to isolate different aspects of eye development. UC researchers are targeting the proteins used in eye development. Manipulating the RNA changes the way genes are expressed, but not the genes themselves. So if the beetles were to reproduce, their offspring would be unaffected.

“When you change the way the lens forms, that should change the way the eye works,” Hassert said. “I’m trying to find out if they can compensate for that, correcting the error I’m inducing.”

Kallia Cooper, undergraduate biology student.

UC biology student Kallia Cooper tends to the insects in professor Elke Buschbeck's lab. Each voracious beetle can eat 800 mosquitoes in its larval stage. Photo/Ravenna Rutledge/UC Creative Services

Dr. Karl Golnik, a neuro-ophthalmologist at UC’s Gardner Neuroscience Institute, said refractive errors are the most common vision deficit in people. This includes shortsightedness, farsightedness and blurred vision called astigmatism.

“We don’t see with our eyes. We see with our brain,” Golnik said. “To have any vision your brain has to be working normally. The signals have to get from your eyes to your brain down your optic nerve.”

Children develop their vision essentially through practice as the brain develops, Golnik said.

Understanding how vision develops in a model system like diving beetles could help medical researchers understand aspects of human eye development. Golnik said researchers are trying to learn more about the genetic relationships of many visual deficits and diseases.

“If they could be discovered in an animal model, that could theoretically lead to a treatment for those things in utero,” Golnik said. “If you don’t do the research, you’ll never know.”

Buschbeck said basic research pushes the boundaries of the unknown, which can lead to unexpected discoveries.

“We’re at the core of understanding these fundamental questions. It’s unpredictable how we might one day benefit from basic research. That’s why it’s really important to do it,” she said.

UC biology professor Elke Buschbeck on her work exploring insect eyes and diving beetles

UC biology professor Elke Buschbeck is studying the incredible eyes of the sunburst diving beetle pictured on a postage stamp on the desktop wallpaper of her computer. Photo/Ravenna Rutledge/UC Creative Services

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