Insects can see the world in much finer resolution than previously thought

September 5, 2017, University of Sheffield
Credit: CC0 Public Domain

Insects have much better vision and can see in far greater detail than previously thought, a new study from the University of Sheffield has revealed.

Scientists have long believed insects would not see fine images. This is because their typically consist of thousands of tiny lens-capped 'eye-units', which together should capture a low-resolution pixelated image of the surrounding world.

In contrast, the human eye has a single lens, which slims and bulges as it focuses objects of interests on a retinal light-sensor (photoreceptor) array; the megapixel "camera chip" inside the eye. By actively changing the lens shape, or accommodating, an object can be kept in sharp focus, whether close or far away. As the lens in the human eye is quite large and the retinal photoreceptor array underneath it is densely-packed, the eye captures high-resolution images.

However, researchers from the University of Sheffield's Department of Biomedical Science with their Beijing, Cambridge and Lisbon collaborators have now discovered that insect compound eyes can also generate surprisingly high-resolution images, and that this has much to do with how the photoreceptor cells inside the compound eyes react to image motion.

Unlike in the , the thousands of tiny lenses, which make the compound eye's characteristic net-like surface, do not move, or cannot accommodate. But the University of Sheffield researchers found that photoreceptor cells underneath the lenses, instead, move rapidly and automatically in and out of focus, as they sample an image of the world around them. This microscopic light-sensor "twitching" is so fast that we cannot see it with our naked eye. To record these movements inside intact insect eyes during light stimulation, the researcher had to build a bespoke microscope with a high-speed camera system.

Remarkably, they also found that the way insect compound eye samples an image (or takes a snapshot) is tuned to its natural visual behaviours. By combining their normal head/eye movements - as they view the world in saccadic bursts - with the resulting light-induced microscopic cell twitching, the insects, such as flies, can resolve the world in much finer detail than was predicted by their compound eye structure, giving them hyperacute vision.

The new study, published today (5 September 2017) in the journal eLife, changes our understanding of insect and human vision and could also be used in industry to improve robotic sensors.

Mikko Juusola, Professor of Systems Neuroscience at the University of Sheffield and lead author of the study, said: "From humans to insects, all animals with good vision, irrespective of their eye shape or design, see the world through fast saccadic eye movements and gaze fixations.

"It has long been known that fast visual adaptation results in the world around us fading from perception unless we move our eyes to cancel this effect. On the other hand, fast eye movements should blur vision which is why it has remained an enigma how photoreceptors work with eye movements to see the world clearly.

"Our results show that by adapting the way sample light information to and gaze fixations, evolution has optimised the visual perception of animals. "

The findings of the study, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), show photoreceptors resolve small moving objects, even at high speeds, far better than predicted by compound eye optics and reveal the mechanisms behind this remarkable hyperacuity.

Professor Juusola said: "By using electrophysiological, optical and behavioural assays with mathematical modelling we have demonstrated that fruit flies (Drosophila) have much better vision than scientists have believed for the past 100 years."

The team of scientists are now testing whether similar processes are happening in the compound eyes of other insects, and also in vertebrates.

Explore further: Fifteen shades of photoreceptor in a butterfly's eye

Related Stories

Fifteen shades of photoreceptor in a butterfly's eye

March 8, 2016

When researchers studied the eyes of Common Bluebottles, a species of swallowtail butterfly from Australasia, they were in for a surprise. These butterflies have large eyes and use their blue-green iridescent wings for visual ...

Acute artificial compound eyes

May 28, 2008

Insects are a source of inspiration for technological development work. For example, researchers around the world are working on ultra-thin imaging systems based on the insect eye. The principle of hyperacuity has now been ...

Evolution of fan worm eyes

August 1, 2017

Scientists examining the multiple eyes found on the tentacles of fan worms have discovered they evolved independently from their other visual systems, specifically to support the needs of their lifestyle.

Recommended for you

Solving the jet/cocoon riddle of a gravitational wave event

February 22, 2019

An international research team including astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has combined radio telescopes from five continents to prove the existence of a narrow stream of material, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.