Bee rhythms more affected by social interactions than sunlight

The important role of light in adjusting the circadian rhythm to the local environment has long been emphasized in studies on individually-isolated animals in laboratories.

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September 24, 2016 23:47
Bee

Bee [Illustrative]. (photo credit: INGIMAGE)

A Hebrew University field study has shown for the first time that social time cues override the influence of light and darkness in regulating the natural body clock of honeybees, highlighting the complexity of clock regulation in the natural habitat.

Circadian rhythms are internal clocks that determine many of an organism’s daily rhythms such as sleep-wake, feeding, urinary output and hormone production. Aligned with the environment by external forces such as sunlight and ambient temperature, circadian rhythms are important for the animal’s health and survival. Disturbances of the circadian clock can result in a variety of diseases in humans and animals, including cancer, mental illnesses and metabolic disorders such as diabetes and obesity.

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The important role of light in adjusting the circadian rhythm to the local environment has long been emphasized in studies on individually-isolated animals in laboratories.

Interactions with others of the same species, while very important for animal survival and fitness in nature, are not considered important external stimuli that affect the animal circadian clock.

But now, a study conducted by researchers from the Hebrew University of Jerusalem and published in the journal Nature Communications challenges this view. The researchers performed a set of large-scale experiments in which they manipulated social interactions and light exposure for more than 1,000 honeybees in cages or in freely foraging colonies housed in observation hives, allowing research in an ecologically relevant context. Every experiment was repeated two to four times, each with bees from a different source colony (which were genetically different).

“We show for the first time that social time cues stably adjust the clock, even in animals experiencing conflicting light exposure and social cycles,” said Prof. Guy Bloch from the ecology, evolution and behavior department at the Hebrew University’s Alexander Silberman Institute of Life Sciences, who led the study.

The researchers collected a massive data set that showed that in honeybees, social interactions can override potent light exposure as external cues that influence the biological clock.

Resetting the circadian rhythm by manipulating the social environment had a significant and stable effect for several days even for two-day-old bees, which are typically active around the clock with no overt circadian rhythms. Young bees that experienced conflicting light and social cycles showed a phase that was more similar to the social cycle. When removed from the hive and monitored individually in constant laboratory conditions, they maintained the phase of the social cycle, meaning that this potent social factor does not depend on physical contact with other bees in the colony.

“This study … emphasizes the importance of studying circadian rhythms in a species-specific, ecologically-relevant context,” said Bloch.

Social insects are ecologically important and offer attractive model systems for studies on the interplay between social behavior and circadian rhythms. The best evidence for the influence of social activity on the internal clock is found in dark cavity-dwelling social animals, such as bees and bats.

This study adds to recent research showing the circadian rhythms in complex natural environments may profoundly differ from those in controlled laboratory conditions.

“Studies in the real world will provide a better understanding of the function and regulation of biological clocks,” said Bloch. It could also contribute to the research on sleep and behavioral disorders, as well as for the understanding of the complex life of bee societies.

TRANSPARENT WOOD WINDOWS COOLER THAN GLASS

Windows made of transparent wood could provide more even and consistent natural lighting and better energy efficiency than glass, according to a just-published paper published in Advanced Energy Materials. The team found that their transparent wood provides better thermal insulation and lets in nearly as much light as glass, while eliminating glare and providing uniform and consistent indoor lighting The transparent wood lets through just a little bit less light than glass, but a lot less heat, said Tian Li, the lead author of the new study. “It is very transparent, but still allows for a little bit of privacy because it is not completely see-through. We also learned that the channels in the wood transmit light with wavelengths around the range of the wavelengths of visible light, but that it blocks the wavelengths that carry mostly heat,” said Li.

The team’s findings were derived, in part, from tests on tiny model house with a transparent wood panel in the ceiling that the team built. The tests showed that the light was more evenly distributed around a space with a transparent wood roof than a glass roof. The channels in the wood direct visible light straight through the material, but the cell structure that still remains bounces the light around just a little bit, a property called haze. This means the light does not shine directly into your eyes, making it more comfortable to look at.

Transparent wood still has all the cell structures that comprised the original piece of wood. The wood is cut against the grain, so that the channels that drew water and nutrients up from the roots lie along the shortest dimension of the window. The new transparent wood uses theses natural channels in wood to guide the sunlight through the wood. As the sun passes over a house with glass windows, the angle at which light shines through the glass changes as the sun moves. With windows or panels made of transparent wood instead of glass, as the sun moves across the sky, the channels in the wood direct the sunlight in the same way every time.

Working with transparent wood is similar to working with natural wood, the researchers said. However, their transparent wood is waterproof due to its polymer component.

It also is much less breakable than glass because the cell structure inside resists shattering.

The research team has recently patented their process for making transparent wood. The process starts with bleaching from the wood all of the lignin, which is a component in the wood that makes it both brown and strong. The wood is then soaked in epoxy, which adds strength back in and also makes the wood clearer. The team has used tiny squares of linden wood about 2 cm x 2 cm, but the wood can be any size, the researchers said.


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