Empty Calories

Bee Informed.jpg

By Dan Wyns July 2, 2019

Foragers gathering fresh sawdust. Photo: Mike Connor

Foragers gathering fresh sawdust. Photo: Mike Connor

Somewhere early on in a “Beekeeping 101” class you’ll learn that honey bees forage for 4 things: nectar, pollen, propolis, and water. The nectar and pollen become honey and bee bread to provide sustenance. Propolis is used as a structural component and also contributes to colony health through immunological activity. Previous blog posts about propolis here and here provide more information. Water is necessary for a variety of purposes including preparation of brood food and evaporative cooling. So in addition to water, bees need 3 substances produced by plants. But do they collect anything else? Of course they do. If you’ve ever seen open syrup feeding, it’s apparent that the bees will forego the flower visitation part of foraging when a sweet liquid is provided. Bees will also readily gather pollen substitute when bulk fed in powder form. While these nectar and pollen surrogates may not be as attractive or nutritious as the genuine articles they are intended to replicate, they can be important in getting colonies through lean times.

Flowers and their surrogates are what the bees should be getting into, but what are they actually getting into? Some beekeepers have a perception that if bees gather it they must need it, but in my time working in and around bees I’ve seen them get into a lot of different things that probably aren’t great for them. One summer we noticed a propolis traps in a yard were yielding a dark brown, almost black propolis with sharp plastic smell instead of the typical red/orange sweet smelling propolis for the area. When we  sat waiting for the construction worker with the Stop/Go sign to allow us through the roadworks where a new topcoat of asphalt was being applied, we noticed bees collecting road tar to use as propolis. This paper detected petroleum derived molecules that matched the chemistry of local asphalt in propolis from urban colonies, confirming that bees will gather sticky stuff other than plant resins. I’ve also seen bees appearing to collect silicon-based caulking product. I’ve often described the physical role of propolis in the colony as bee-glue or caulking, so seeing one bee resort to gathering our version shouldn’t come as a shock if actual resins aren’t available. Bees gather “real” propolis from a variety of botanical sources depending on geography and climate. Some of the most common propolis sources in temperate climates are members of the genus Populus which includes poplars, aspens, and cottonwoods. For more about the role of propolis in the colony and an overview of botanical sources around the world, check out this article.

It’s not just propolis collection where bees make mistakes, sometimes they get it wrong when seeking pollen too. While building woodware in the shop, I’ve seen bees take a lot of interest in the sawdust from both treated and untreated lumber. I’ve never actually seen a forager pack it onto her corbicula, but beekeepers report bees gathering a variety of powdery materials when pollen is scarce. An early study on pollen foraging noted this tendency,  “During periods of pollen scarcity bees are reported to seek substitutes, such as bran, sawdust, and coal dust, which are of no known value for brood rearing.

Just about any sweet liquid is going to get the attention of honey bees, and I’ve seen them investigate many kinds of sodas and juices. This tendency may be a little unnerving to picnickers, but it isn’t really a problem unless there is a more permanent stationary source of sugary liquid that the bees find. One such case happened when some urban bees in NYC found a bit of runoff syrup from a maraschino cherry factory which was only the beginning of the story.

https://beeinformed.org/2019/07/02/empty-calories/

Earning a Bee's Wings

Washington State University-St. Louis (The Source) By Talia Ogliore February 20, 2019

In hives, graduating to forager a requirement for social membership

It is a classic coming-of-age story, in many ways.

A honey bee hatches and grows up deep inside a hive. Surrounded by 40,000 of her closest relatives, this dark and constantly buzzing place is all that she knows. Only after she turns 21 days old does she leave the nest to look for pollen and nectar. For her, this is a moment of great risk, and great reward.

It’s also the moment at which she becomes recognizable to other bees, according to new research from Washington University in St. Louis. A study in the journal eLife reports that honey bees (Apis mellifera) develop different scent profiles as they age, and the gatekeeper bees at the hive’s door respond differently to returning foragers than they do when they encounter younger bees who have never ventured out before.

This work offers new insight into one of the most important interactions in the lives of social insects: recognizing self and other

Ben-Shahar

Ben-Shahar

Until this point, most bee researchers thought bees recognize and respond to a scent that is the homogenized scent of all of the members of their own colony. That’s how it works for some ants and other insects, at least. But new work from the laboratory of  Yehuda Ben-Shahar, associate professor of biology in Arts & Sciences, shows that nestmate recognition instead depends on an innate developmental process that is associated with age-dependent division of labor. The work was completed in collaboration with researchers from the lab of Joel Levine at the University of Toronto.

“It was always assumed that the way that honey bees acquire nestmate recognition cues, their cuticular hydrocarbon (CHC) profiles, is through these mechanisms where they rub up against each other, or transfer compounds between each other,” said Cassondra L. Vernier, a graduate student at Washington University and first author of the new study.

“You would expect, then, that even younger bees would have a very similar pheromonal profile as older bees. When in fact that is not what we saw,” she said.

Vernier compared the CHC profiles of bees on the day they were born and at 1 week, 2 weeks, and 3 weeks old. The 3-week-old bees had significantly different profiles than their younger siblings.

Graduate student Cassondra Vernier conducted lab experiments and observed hours of bee interactions at the entrance to the hive. She is shown here at Tyson Research Center, Washington University’s environmental field station. (Courtesy photo)

Graduate student Cassondra Vernier conducted lab experiments and observed hours of bee interactions at the entrance to the hive. She is shown here at Tyson Research Center, Washington University’s environmental field station. (Courtesy photo)

Vernier compared the CHC profiles of bees on the day they were born and at 1 week, 2 weeks, and 3 weeks old. The 3-week-old bees had significantly different profiles than their younger siblings.A 3-week-old foraging bee also has a very different job to support the hive than a younger bee — one who spends her time as a nurse caring for bee larvae and building the waxy honeycomb structures in the hive.

The researchers wanted to separate out whether the differences they saw were based on age alone, or were somehow tied to the older bees’ foraging activities. Bees that exit the hive to collect nectar encounter lots of scents on flowers and other surfaces they touch. They also are exposed to different environmental factors such as sunshine and rain that could affect their body coatings.

So Vernier also compared the CHC profiles of foraging-age bees that were held in the hive and not permitted to forage with bees that were able to venture out. These two groups were also significantly different.

“What we found is that it’s actually a combination of both — of being at the age for foraging, and actually performing the foraging activities,” said Ben-Shahar.

Guards are gatekeepers; specific triggers still unknown

Importantly, not every bee notices the difference in scent profiles. Guard bees are the only ones who care to identify outsiders.

“They sit in the entrance and they have a very specific posture,” Ben-Shahar said of the guards. “They’re very attentive. Their forelegs are usually raised, and they’re very alert. Still, it is hard to know who they are until they react to somebody.”

Place a 1-day-old, 1-week-old, or 2-week-old outsider on the stoop in front of a guard, and she is likely to be able to waltz on through. But it’s a different story after 3 weeks of age — when guards bite, sting and/or drag outsiders away from the door.

“Nestmate recognition is something that is very context-specific. It involves an interaction between very specific bees within the colony,” Ben-Shahar said. “Most bees are completely oblivious. Most colony members don’t produce the signal that tells anyone if they belong or not, and they don’t care about the signal. They don’t react to it.”

As an important caveat, the new study does not directly address the mechanism by which cue specificity is determined in bees. Which specific components of the honey bee CHC profile represent the nestmate recognition cue remains unknown.

“Something environmentally related is causing expression-level changes in the CHC profiles of the bees,” Vernier said. “That’s our model for now.”

The bees in this study were kept in two different locations: Tyson Research Center, the environmental field station for Washington University in St. Louis, and an amateur beekeeper’s private residence in University City, MO.

Funding for the project was provided by the National Science Foundation under grants NSF DGE-1143954, IOS-1322783, IOS-1707221 and IOS-1754264.

https://source.wustl.edu/2019/02/earning-a-bees-wings/

Forager bees ‘turn on’ gene expression to protect against microorganisms, toxins

UC Davis News & Information   November 9, 2015

Forager bees, like this one feeding on lavender nectar, "turn on" genes that could help protect the hive and honey against microbes and toxins. (Kathy Keatley Garvey)When honeybees shift from nurse bees to foragers, or from caring for the brood to foraging for nectar and pollen, the bees “turn on” gene expression with products that protect against microorganisms and degrade toxins, three University of California, Davis, scientists have discovered.

Their findings on bee immunity and toxin metabolism are published today inScientific Reports by the Nature Publishing Group.

“First, the results suggest that forager bees may use antimicrobial peptides — short sequences of amino acids with general activity — to reduce microbial growth in stored food resources,” said Rachel Vannette, assistant professor, UC Davis Department of Entomology and Nematology. “This would be a largely unrecognized way that bees protect honey and potentially other stored resources from microbial spoilage. Second, this work shows that forager bees produce toxin-degrading enzymes in nectar-processing tissues.

“This may allow forager bees to degrade many different kinds of compounds in nectar, before it is stored,” Vannette said. “Bees also vary in their ability to do this; foragers have a greater ability to degrade a variety of compounds than nurses. This may have implications for hive health and management.”

The scientists found the change in the bees’ nectar-processing tissues, but not in the gut. The scientists surmised that the exposure to bacteria or yeasts in the environment may trigger this change, but they did not examine it in the study.

“It had been well known that the division of labor in a honeybee colony is supported by extensive differences in brain gene expression between bees that perform different jobs,” said Gene Robinson, director of the Institute for Genomic Biology and Swanlund Chair of Entomology, University of Illinois at Urbana-Champaign, who was not involved in the research. “This new research shows nicely that this genomic differentiation extends beyond the brain; different complements of active genes in a variety of tissues make each bee better suited for the job it needs to perform.”

The journal article, titled “Forager Bees (Apis Mellifera) Highly Express Immune and Detoxification Genes in Tissues Associated with Nectar Processing,” is the work of senior author Brian Johnson, assistant professor, UC Davis Department of Entomology and Nematology; and co-authors Abbas Mohamed, graduate student researcher in the Johnson lab and a member of the Pharmacology and Toxicology Group, and Vannette, who joined the UC Davis Department of Entomology this fall after serving a postdoctoral fellowship at Stanford University. At Stanford, Vannette examined the role of nectar chemistry in community assembly of yeasts and plant-pollinator interactions.

Johnson, whose research interests include animal behavior, evolution, theoretical biology and genomics, recently began long-term research on the honeybee immune system and the causes and consequences of economically important diseases or syndromes such as colony collapse disorder.

The team plans to follow up with functional assays to examine the potential of these gene products to reduce microbial growth and degrade a variety of natural and synthetic compounds.

Read at: http://news.ucdavis.edu/search/news_detail.lasso?id=11361