A new study by researchers at the University of Adelaide and Lund University that appears online today in the journal Scientific Reports suggests that honey bees have much better vision than previously thought.
A western honey bee (Apis mellifera) in Nagakute, Aichi, Japan. Image credit: Emran Kassim / CC BY 2.0.
Bee vision has been studied ever since the pioneering research of Dr. Karl von Frisch in 1914, which reported bees’ ability to see colors through a clever set of training experiments.
“Today, honey bees are still a fascinating model among scientists, in particular neuroscientists,” said lead author Dr. Elisa Rigosi, a postdoctoral researcher at Lund University, Sweden.
“Among other things, honey bees help to answer questions such as: how can a tiny brain of less than a million neurons achieve complex processes, and what are its utmost limits?”
“In the last few decades it has been shown that bees can see and categorize objects and learn concepts through vision, such as the concept of ‘symmetric’ and ‘above’ and below’.”
“But one basic question that has only been partially addressed is: what actually is the visual acuity of the honey bee eye? Just how good is a bee’s eyesight?”
“Previous researchers have measured the visual acuity of bees, but most of these experiments have been conducted in the dark,” added co-author Dr. Steven Wiederman, of the University of Adelaide.
“Bright daylight and dark laboratories are two completely different environments, resulting in anatomical and physiological changes in the resolution of the eye.”
“Photoreceptors in the visual system detect variations in light intensity,” Dr. Wiederman explained.
“There are eight photoreceptors beyond each hexagonal facet of a bee’s compound eye, and their eyes are made out of thousands of facets!”
“Naturally, we expected some differences in the quality of bees’ eyesight from being tested in brightly lit conditions compared with dim light.”
The team set out to answer two specific questions:
(i) what is the smallest well-defined object that a bee can see?
(ii) how far away can a bee see an object, even if it can’t see that object clearly?
To do so, the researchers took electrophysiological recordings of the neural responses occurring in single photoreceptors in the eyes of western honey bees (Apis mellifera), also known as European honey bees.
They found that in the frontal part of the eye, where the resolution is maximized, honey bees can clearly see objects that are as small as 1.9 degrees – that’s approximately the width of your thumb when you stretch your arm out in front of you. This is 30% better eyesight than has been previously recorded.
“In terms of the smallest object a bee can detect, but not clearly, this works out to be about 0.6 degrees – that’s one third of your thumb width at arm’s length. This is about one third of what bees can clearly see and five times smaller than what has so far been detected in behavioral experiments,” Dr. Rigosi said.
“These new results suggest that bees have the chance to see a potential predator, and thus escape, far earlier than what we thought previously, or perceive landmarks in the environment better than we expected, which is useful for navigation and thus for survival.”
This work offers new and useful information about insect vision more broadly as well as for honey bees.
“We’ve shown that the honey bee has higher visual acuity than previously reported,” Dr. Wiederman said.
“They can resolve finer details than we originally thought, which has important implications in interpreting their responses to a range of cognitive experiments scientists have been conducting with bees for years.”
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Elisa Rigosi et al. 2017. Visual acuity of the honey bee retina and the limits for feature detection. Scientific Reports 7, article number: 45972; doi: 10.1038/srep45972
