Sometimes I ask the universe a question and it decides to give me the answer before I even get around to googling it.
Being late winter/early spring (1 month until equinox!!!!) it is time to check our hives and if need be, feed them. Avoiding the whole discussion on feeding bees (to sum up: good beekeepers leave more than enough winter food and should therefore not worry about starvation vs $*#! happens so check and feed anyhow, thanks) and getting to the nitty gritty, here is the advice is coming out:
Crack lid, remove inner cover, 2 shims, lay down wax paper, add dry white sugar, replace lids. Note that spring feeding is different: we make sugar syrup by adding water in a certain proportion. Same with autumn feeding (different proportions) to top off reserves.
By now all the organic beekeepers should be howling. WHITE SUGAR. That’s Enemy Territory. White refined sugar is the Michael Jackson of the carbohydrate world: bleached beyond all recognition of what it should have been with a breathtaking array of chemicals. While those chemicals do not end up in the final product (otherwise we’d have poisoned ourselves to death long ago) the by-products of the refining process, the agricultural practices of cane sugar plantations and human rights issues in the industry should be enough to give beekeepers (or any human) pause. Why buy products that lean heavily on the pesticides that are killing our bees? (Answer: it is cheap, plentiful and it we like to think the sugar industry issues are not our problem.)
And yes I know that feeding honey back to bees has its own issues so I will say it here: never feed honey taken from one hive to another, because you do not know if you are contaminating a recipient healthy hive with spores, fungus, molds, disease or what-not from the donor. If you want to feed honey pulled from a hive in fall to that same hive in spring go for it, just label everything so you do not get confused.
Now with all those qualifiers out of the way, here comes the million dollar question (literally) and all the other questions that the scientist in my soul wants to know.
Question: Why is refined white sugar, aka table sugar, aka sucrose (C12H22O11) considered so bad to feed to bees when sucrose can be found in nectar (and therefore in the finished, evaporated product, aka honey?)
I am probably not actually going to answer that question. At least, directly. There, I’ve warned you. My brain jack-rabbitted ahead of this one and asked a whole bunch of other questions:
1. Why do flowers produce an array of sugars in their nectar and not just one? Is it a byproduct issue, or diversity at work, and how metabolically expensive is that for the plant?
2. When bees actually ingest nectar for energy, what is the metabolic breakdown that happens? Where does the energy go?
3. Is one sugar better than another for wax production, brood rearing and ‘bee health support’?
4. If we knew the answer to all the above questions, here comes the next bunch:
a) Do some flowers have better nectar ingredients than others?
b) If there was a perfect nectar out there for bees, which flower would it come from?
c) Is there anything a gardener can do (soil amendment manipulation, traditional cross-breeding, etc) to improve a nectar profile for bees without venturing into frankenflower territory?
d) Let’s say I have no choice but to use table sugar in an emergency. Do I add something to it (like essential oils, vitamins or whatnot?)
It is always easy to ask questions. Not so easy to find reliable answers. I should be in my basement working on renos right now… Ok internet, help me out.
We know bees have 2 stomachs: one we call the honey crop, for nectar storage, and the other that is connected to the rest of its digestive system. How much nectar can its stomach hold? (Answer, 70 milligrams, which is a lot considering a honeybee weighs 80 milligrams.) Does a little go a long way? (No it does not; foragers will not only eat honey at home but sip nectar on the go.)
Honey is a downstream product of nectar with bee enzyme additives, so I will skip the much-repeated honey research and get into nectar. Enter Wikipedia’s nectar entry.
Nectar comes from nectaries in angiosperms (flowering plants). The sugar breakdown is roughly 55% sucrose, 24% glucose and 21% fructose and a ‘brew’ of other chemicals (under the wide umbrella secondary metabolites) that are not refined out of honey. Nectar is ‘thin’ in the sense that most of it is comprised of water; only 5-20% of nectar is sugar.
I should first break the discussion down into useable sugars and non-useable ones. Sugars are hexalose carbon rings that many plants and animals use for energy. The rings can be alone (monosaccharides) or joined together in 2 or more series (di or polysaccharides). Each sugar name denotes a different sugar. Bees cannot use disaccharides as-is; they must break them into monosaccharides, because only monosaccharides can pass through the mid-gut wall into the bee’s hemolymph (bee-blood) for later use by cells.
Bees can use sucrose, glucose, fructose, mannose, maltose and melezitose but flowers do not produce the last three in large quantities. (I think). Rhaminose, xylose, arabinose, galactose, mannose, lactose, raffinose and dextrin sugars cannot be used by honeybees. Note that fructose can also be called invert sugar because of its structural composition.
Now hop over to the NIH archives…
The honeybee genome was sequenced in 2006, and boy did we learn a lot. The process of breaking down sugar is called glycolysis, and it is a highly conserved process across all species, genetically speaking. Why it is done: for energy! The scientific term is cellular respiration. Basically, chopping up sugar rings results in pyruvate and chemical energy in the form of bound phosphates (called ATP!) The whole glycolytic cycle keys into several other important chemical pathways (if you recall the Krebs Cycle/Citric Acid cycle from school, this is what I am referring to. I will not repeat it here.)
Honeybees have 174 genes that code for carbohydrate-metabolizing enzymes, and 28 more to deal with lipids (another fascinating story, so is the fat body.) All that coding is amazing, and so are the enzymes. I’m only going to deal with a few but there is an ocean of info on them out there.
As soon as bees take a sip of nectar their salivary glands are hard at work: they produce the enzyme invertase (also called diastase), which converts sucrose (a disaccharide) into glucose and fructose (the monos). Invertase is also found in the honey crop, the first stomach.
Oh, cut away from sugar and into bee biology for a second: there is a proventricular valve between the crop and the true stomach (the midgut), followed by a small and large intestine before reaching the anus. Food passage (think pollen) requires 2-2.5 hrs from one end to the other, and it is the pollen shells that are ejected as the rain of green poo on beekeepers.
Ok, recue the sugars. Sugars are absorbed from the gut wall into the hemolymph, and the 3 main ones found there are glucose, fructose and the disaccharide trehalose. Gasp, yes, a disaccharide; it is 2 glucoses joined together (BTW, a great antioxidant and hydrator) and it is made by enzymes in the blood, so chill out, no rules are broken. Trehalose is a used as mobile carb storage since it is easy to snap apart into 2 glucoses again.
Fructose metabolism does not follow the same path as glucose. I know that in humans it is dealt with by the liver and kidney. In honeybees – I have no idea. I could not casually find anything that made much sense, though I stared at a diagram for a little bit. I just left it alone for the sake of my sanity,. Though I did learn I could order all sorts of gene bits from biocompanies like GenScript that drew from a huge genetic databank called KEGGS. Uber-cool stuff, but they would not name prices outright.
Anyhow, the more I read the more I realized that most immediate nectar consumption goes toward the perpetuation of flight during foraging. We forget that honeybees are exothermic –they lose heat to the environment very fast, and they have to maintain a body temperature (thermoregulation) that will allow their flight muscles to work, as well as general locomotion! (Back to this later.) They also require energy for rapid sensory processing and will consume up to 70% more oxygen while foraging to aid faster glucose metabolism. They only have a limited ability to store glucose as glucagon in their muscles and use very little fat or amino acids for flight fuel; nectar really is the stuff of life for them. Flight muscle mass is about 75% of the entire thorax weight, and it turns out their energy turnover rate in their flight muscles is 3x faster than a hummingbird and 30x faster than top human athletes. Phew.
Here is another note on nectar: scientists studying bumblebees found that warm nectar that has less sugar in it is still preferable to a more sugar-rich nectar at a cooler temperature. Why? Because bees can use the heat from the water portion to maintain foraging flights. That is how important body temperature regulation becomes in maintaining foraging flights.
Metabolic regulation extends into other areas of a bee’s life: it helps determine caste and behaviour in bees. You already know this: feed a larvae a royal jelly-rich diet and it becomes a queen. Less rich, you get a worker. The wherefore and why lies within the metabolic processes (which is a whole other post).
On to question 3, then. Which sugar source is better? I’ll talk super-briefly about 3: honey/nectar, white sugar (sucrose) and high fructose corn syrup (HFCS.)
There are numerous scientific studies on the efficiency of bee flight and various % of nectar feeding, both in controlled and uncontrolled conditions. Generally any flower that can provide more than 30% sugar in their nectar does foraging bees just fine; they do not experience an premature cap on their maximum metabolic rate for flight use, which as previously stated is is the majority of their entire body’s energy consumption.
Pollen and nectar do more than just provide for metabolic needs, though. They have additional benefits for bees and their health:
A 2013 study by Wenfu Mao and colleagues from the University of Illinois at Urbana–Champaign report that “constituents found in honey, including p-coumaric acid, pinocembrin, and pinobanksin 5-methyl ether, specifically induce detoxification genes.” Yes, detox for bees. P-coumaric acid increases mid-gut metabolism of coumaphos, by about 60%. Coumaphos is a widely used in-hive pesticide used for controlling Varroa destructor mites. So, pesticide detox.
Our pointy-eared logician would also tell us that P-coumaric acid is a major component of pollen. It is part of the natural diet of honey bees and may help regulate immune and detoxification processes.
Those secondary metabolities in nectar include things like non-protein amino acids, vitamins, enzymes, organic acids, alkaloids, phenolics, glycosides, terpenoids, metal ions, and other volatile oils. They all have uses, not just for the plant but for bees, though we understand little of it.
Volatile chemicals can be used powerful attractants to pollinators. Caffeine boosts bees’ memory and so the plant uses it to encourage bees to remember them and return for another visit. Some chemicals are ok for bees but are harmful to humans (like the alkaloids in rhododendrons).
Scientists have found that certain chemicals in plants help bees (bumble and honey) ward off parasites and boost their immune systems; in fact unhealthy bees can change their foreign behaviour to maximize collection of those chemicals. Also, some compounds with anti-parasite function are sought after by bees when they have parasites, but not when they are healthy. (I’ll get back to this later)
On to the other two sugar sources.
HFCS has a similar sugar profile to honey so many thought one could be safely substituted for another. However researchers find HSCF-fed workers have decreased longevity that are HFCS fed and there is a lower spring brood production . HFCS can form toxins in heat (especially during storage) and the pH profile is different to honey.
Researches found that a honeybee’s body can tell the difference between HFCS and nectar. When focused on gene activity in response to feeding with honey, high-fructose corn syrup (HFCS), or sucrose they found that those bees fed honey had a very different profile of gene activity in the fat body (analogous to liver and adipose tissues) than those relying on HFCS or sucrose. Hundreds of genes showed differences in activity in honey bees consuming honey compared with those fed HFCS or sucrose
What this means -sugar is not sugar. Different carbohydrate sources can act differently in the body.
Some of the genes that were activated differently in the honey-eating bees have been linked to protein metabolism, brain-signaling and immune defense. Some substances in honey increase the activity of genes that help the bees break down potentially toxic substances such as pesticides.
Another report: gene activated differences between HFCS and sucrose diets were much more subtle and included a few genes involved in carbohydrate and lipid metabolism.
In short, bees receive nutritional components from honey that are not provided by alternative food sources (HFCS and sucrose) widely used in apiculture.
That is hardly an exhaustive review of the topic but it gives you a gist of the research being done.
So, flowers, we’ve made it to question 4. What have you to say for all this? Do you specifically differ in nectar, or are you all one happy homogenous family given optimal soil, sun and rain conditions?
Of course not. Mother Nature does not roll that way.
A visit to another scientific paper told me this:
The ratio of nectar sugars may depend not only on the anatomy of the plant (Doner 1977) but also on the structures that secrete and conduct sugars (Nicolson and Thornburg 2005). Percival (1965) reported that certain families of plants consistently contained hexose-rich (Brassicaecae and Asteracease) or sucrose-rich (Laminaceae and Rannunculaceae) nectars; sucrose and variable levels of other oligosaccharides are the main sugar components in nectar (Maurizio 1976; Doner 1977; Shuel 1992; De la Barrera and Nobel 2004).
Even more interesting: many plants produce sugars that bees cannot use (maybe other pollinators can?) Why make sugar that insects cannot use? Probably because they are byproducts of other processes, not desired endproducts. Evolutionary pathways are messy things, not a Ford assembly plant with 0 waste emissions.
A lot of authors pointed out in their studies that additional sugars found in nectar are non-nutritive because bees are unable to break them down and can become toxic upon ingestion, especially under laboratory conditions (feeding caged bees). To ensure that a balance of nutrition is obtained, bees require a diversity of plant sources on which to forage.
It’s like the flowers know… (no that is not a hypothesis)
Another study points out that enzymes like diastase/amylase that break down starches into less complex sugars are also found in nectar, but in varying amounts from plant to plant. Orange blossoms have very little diastase at 4.25 while buckwheat has 36.8 (sorry, I was not given units in the table, I will assume ppm or something suitably scientific.)
Which goes back to the old question of the chicken and the egg –which came first? The sugar ratio of plants that selected for honeybees with certain genetic/enzyme profiles, or did preferential bee pollination perpetuate the flowering plant genotypes that most appealed to them? Or did it all happen in lock-step?)
The lock-step idea is actually called co-evolution, and it is a common process found among many animal and plant species with some interesting results. Think monarch butterflies and milkweed: they can tolerate the alkaloids but other species cannot.
We have noted that flowers have a lot of secondary metabolites and even talked about bees self-medicating from plants because of them. Research was done to see if any can truly help honeybees. Turns out the tobacco alkaloid anabasine reduced a protozoan gut parasite load in bumblebees by more than 80%. Other compounds that protected bees from parasites included another tobacco alkaloid, nicotine, the terpenoid thymol, found in nectar of basswood trees, and catalpol, an iridoid glycoside found in nectar of turtlehead, a wetland plant of eastern North America.
But this is not about the plant being NICE to the bee; it is a chemical protection and it takes its toll on bees as well. Anabasine, the compound with the strongest anti-parasite benefit, imposed a reproductive cost, increasing the number of days necessary for bees to mature and lay eggs. (Despite this delay, however, there were no differences in ultimate reproductive output in the experiment.)
This research clearly demonstrates that wild bees can benefit when they consume the secondary metabolites naturally present in floral nectar. And bees’ lifetime exposure to these compounds is likely even greater, since they also consume them in pollen and as larva.
I may have said that already, but it is worth repeating. My conclusions are my own, but I am becoming very wary of trying to wedge a large amount of processed sugar between a tight co-evolution of flower and insect.
A few more questions. Just a few. And not by me, but by a USDA NIFA post-doctoral student at the Univerity of Vermont.
Regarding self-medication from plants by honeybees – “Could this research be leveraged to help declining bee populations? We don’t know yet. “ Would planting particular plants around apiaries and farms would result in healthier bee populations? We don’t know yet. Are native plants important sources of medicinal compounds for bees with which they share long evolutionary histories? We don’t know yet. Can farms that depend on wild bee pollinators for delivery of the ‘ecosystem service’ of pollination be better managed to support bee health? We don’t know yet.
But he plans on investigating. Yay science!
I am exhausted. I’m done. Just done. I know I’ve missed something, misspelled something, misrepresented something or just plain got off topic. So be it. It was still a fun romp. Hope you enjoyed it.
My Copious Source Notes, In No Particular Chronological Listing, With Appropriate Annotations For Casual Viewing.
Because I hate people who don’t source their info (and forgive me the single sin of a Wikipedia one), and I also hate the dry, starchy formality of scientific sources. I can live with this balance.
Chronic stress on bees fail to upregulate aggression –an interesting finding. I don’t think I actually talked about this because my blog was getting WAY too long but it is still interesting for a beekeeper to know
Links to the source paper on genes that control glycolysis that in turn affect aggressiveness and maturation of honeybees.
The only video that named actual chemicals used in sugar-making. All other website were either too biased for me to trust them, did not name sources or skipped over the details of the processing.
A good review of bee digestive system and processes. It is too classy to use the word poo or butt.
pgh on how this stuff is good to help bee immune systems
Strap yourself down and skim through this one for some really interesting facts nestled between a lot of scientific jargon. If you are not a geneticist, get a coffee to stay perky.
The nectar differences in plant species paragraph. I will read those after a round of mudding and sanding downstairs tonight.
Bee blood! Sugar blood levels! Apparently there is no such thing as diabetic bees since they cannot deal with insulin or any form of active sugar transport. Also, other great tidbits of metabolic info, including how to aenesthestize a bee without killing it.
Flight muscle metabolism rates and so forth. Biolgy biology etc. This time the bees were sacrficed for science, don’t read that part if you like your bees whole and uncentrifuged.
Paper: Winston ML. The Biology of the Honeybee. Cambridge, MA: Harvard University Press; 1987
Reproductive and behavioural differences and metabolic process regulation.
Info on HFCS on honeybees
LeBlanc BW, Eggleston G, Sammataro D, Cornett C, Dufault R, Deeby T, St Cyr E (26 August 2009). “Formation of Hydroxymethylfurfural in Domestic High-Fructose Corn Syrup and Its Toxicity to the Honey Bee (Apis mellifera)”. Journal of Agricultural and Food Chemistry 57 (16): 7369–7376. doi:10.1021/jf9014526. PMID 19645504.
Says it all in the title.
-both articles deal with diet-dependent gene expression. We are affected by what we eat. We as in honeybees (and humans too)
-the research on coevolution of plant-herbivore interactions as an ‘arms race’ and benefits of certain secondary metabolites on bees regarding parasites and self-medication.
-lists the first note I followed on the benefits of warm nectar temperature. It is sourced in the document but I did not bother following the link to read the whole thing.
The enzyme tables of amylase with the mystery units. Batman will go investigate this someday. Me, I’ll let it remain as is.