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Photo of third instar larva by Annette Stowasser
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University
of Cincinnati researchers are reporting on the discovery of a bug with
bifocals – such an amazing finding that it initially had the researchers
questioning whether they could believe their own eyes. “To the best of
our knowledge, this is the first demonstration of truly bifocal lenses
in the extant animal kingdom,” the researchers state in the Aug. 24
cover feature of the premier life-science journal, Current Biology.
The article is an exploration of two eyes of the larvae of the sunburst diving beetle (Thermonectus marmoratus).
The two eyes have the bifocal lens, which the researchers have found in
four of the larvae’s 12 eyes, says researcher Elke K. Buschbeck, a UC
associate professor of biology.
The
article explains that using two retinas and two distinct focal planes
that are substantially separated, the larvae can more efficiently use
these bifocals, compared with the glasses that humans wear, to switch
their vision from up-close to distance – the better to see and catch
their prey, with their favorite food being mosquito larvae.
“In
addition, we think that within the principle eyes, separate images of
the same object could be focused on each of the two retinas, allowing
each eye to function as ‘two eyes in one,’” the researchers reveal in
the article. The tubular-shaped eyes with the bifocals allow them to
efficiently focus onto their two retinas, says Annette Stowasser, a UC
biology doctoral student and first author on the paper.
The
discovery was made in Buschbeck’s lab and was supported by her National
Science Foundation CAREER award to recognize the research and teaching
talent of young faculty. “We’re hoping this discovery could hold
implications for humans, pending possible future research in biomedical
engineering,” Buschbeck says.
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Photo of head of third instar larva by Elke Buschbeck
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“The discovery could also have uses for any imaging technology,” adds Stowasser.
The
sunburst diving beetle larvae that was studied typically live in creeks
and streams around Arizona and the western United States. It’s
classified as a holometabolous insect – the group of insects that morph
into something completely different from how they originated – like the
caterpillar/moth or the maggot/fly. The larvae of these beetles have the
bifocal lens. They lose these intricate lenses when they become a
beetle.
As
the researchers zeroed in on how the multiple eyes of this insect
worked, they did even more research to try to disprove what they saw.
They first used a microscope to look through the lenses of the two eyes
detailed in the research article. They saw how the lens could make a
second image grow sharper – something that could only happen with a
bifocal.
“It
was my first research project, and I seriously thought I made a
mistake, and then we did additional research to try to kill the
hypothesis,” says Stowasser. However, their findings were confirmed with
more research in addition to observing the operation of the lens and
the two focal planes via a microscope. They saw the bifocal again when
they used a method to project a narrow light beam through the lens. “Our
findings can only be explained by a truly bifocal lens,” write the
researchers.
Contributing
researchers included Alexandra Rapaport, a UC undergraduate
neuroscience major; John E. Layne, UC assistant professor of biological
science; and Randy C. Morgan, Invertebrate Conservation program manager
for the Cincinnati Zoo & Botanical Garden.
The
UC research was supported by Buschbeck’s $805,000 CAREER award from the
National Science Foundation, which was awarded in 2005.
The
researchers thank the Cincinnati Zoo and Botanical Garden for providing
the original population of sunburst diving beetles for the research.
Read the online journal article
UC Research
McMicken College of Arts and Sciences
Original article
