麻豆淫院

The hunt for nectar can take honeybees kilometers away from their hive into unknown territory鈥攁nd yet, they always find their way back. The sun's position in the sky serves as a kind of compass for bees, even when clouds or other objects block it from view. They owe this ability to the special structure of their complex eyes, which they use to analyze patterns of polarized light in the sky that are invisible to humans.

A research team from the University of Konstanz and the University of Ljubljana has shed light on the visual properties of this specialized part. In their recent study in Biology Letters of the Royal Society Publishing, the team examines how some light detector cells in bees' eyes are connected to each other. They discovered that in the skyward-facing area of the bee's eye, a signal received by one cell also appeared in others. This unexpected connection produces a less-detailed but more accurate image of polarized light in the sky.

One facet among many

Unlike the human eye, in which a single lens focuses the light from the environment onto our visual cells, bees' eyes are comprised of thousands of individual facets (ommatidia), each one with its own lens. These are known as complex eyes. In the case of bees, the complex eyes contain different specialized areas.

"Most of the facets provide a sharp image of the surroundings. However, the upper region of the eyes contains a group of ommatidia that operate differently and are responsible for detecting polarized light in the sky. We took a closer look at this area," explains Georgios Kolyfetis, co-author of the study. Kolyfetis is a doctoral researcher from James Foster's research team in the Department of Biology at the University of Konstanz

"Light-detecting cells in each of these upper facets are less sensitive than in the facets elsewhere. This keeps bees from getting blinded as they use this part of their eyes to look at the daytime sky," he adds.

This is clearly useful, yet it comes at a cost: The reduced sensitivity of these facets prevents bees from detecting subtle changes in the sky.

"While they see the rest of the world in more detail, bees see the sky more like a watercolor painting in which adjacent brush strokes blend into each other and details are hidden," explains James Foster, who led the study. "But this is exactly what makes this part of the eye particularly good at detecting large-scale polarization patterns in the sky."

Working together to get the full picture

To understand this, it is worth taking a look at how the human eye works. Our eyes focus light onto individual pixels and use them to construct an overall picture. At night or in poor lighting, this precise sight is no longer possible. The human eye compensates by combining multiple pixels together.

A loss of detail is the trade-off for amplifying the light signal. Scientists call this process "spatial summation." This study reveals that the upper group of facets in bee eyes work together in the same way鈥攁nd around the clock, not just at night.

However, the function is not exactly the same. "In mammalian and human eyes, nerve cells combine the signals of multiple light receptors and send the joint signal on to the brain. In the case of bees, some of the light cells are directly connected to each other," explains neurobiologist Gregor Belu拧i膷 from the University of Ljubljana. "Each individual facet thus also responds to what neighboring facets see."

Seeing what's important

What purpose does this serve? The blurry image of the space above them can help bees to tune out unimportant information and only focus on the big picture.

"Bees register and analyze the polarization pattern of light in the sky. Based on this information, they determine the sun's position and align their inner compass accordingly. They simply blend out disruptions like clouds or branches overhead," Kolyfetis concludes.

Discovering this function in bee eyes is interesting not only from a biological perspective, but it could be used to further develop modern technologies.

"Autonomous vehicles could also benefit from this strategy for navigation. Cameras pointed at the sky could serve as a kind of backup compass if GPS and magnetic signals are unreliable or fail," Foster says.

Since bees are able to perform this feat with a small group of facets, "artificial bee eyes" could provide an inexpensive way to supplement other autonomous navigation systems.