The Miracle Molecule
Ed Erwin
Credit for this article goes primarily to Randy Oliver and his non-profit organization ScientificBeekeeping.com. Randy started beekeeping as a hobby around 1966, and then went on to get university degrees in biology sciences, specializing in entomology. I highly recommend using Randy’s website as a resource, and while you’re there, contribute to his organization.
Randy wrote two articles in 2007 about vitellogenin which prompted me to try to understand and summarize the benefits of vitellogenin in honey bees.
If you’re like me, you’ve probably never heard of vitellogenin and its benefits, but it is critical to the survival of honey bees. You will soon learn the benefits. Vitellogenin molecules are deposited in fat bodies in the head and abdomen of the bees and act as a lipoprotein storage reservoir. This primarily occurs in the form of the compound called “vitellogenin.” Its main component is protein (91%) with a bit of sugar (glycol, 2%) and fat (lipo, 7%). As we know, pollen is a valuable resource of protein for honey bees and research has shown that bees are genetically biased to collect pollen containing high levels of vitellogenin. Bees also collect pollen from a variety of plants. The selection and variety of pollen gathered is vital because the pollen varies in its composition of amino acids, which are the building blocks for protein. When pollen is unavailable, or the availability is low, the nurse bees in the bee colony have use of a reserve of vitellogenin to sustain the young and secrete brood food. Foragers are only fed enough protein to keep them working to collect nectar and pollen. Vitellogenin also enhances the immune system and increases the lifespan – particularly in the queen and Winter fat bees.
We’ve all heard of Winter bees, royal jelly and the length of time a queen can live. It is the molecule vitellogenin that makes this phenomenon possible. This stored up protein reserve also allow the nurse bees to secrete brood food in the spring – even in the absence of new pollen.
During the first three days of both the queen and worker bee’s life ,they are fed royal jelly. The worker larvae are subsequently fed a mixture of royal jelly, pollen and honey. Royal jelly is a lipid-rich mixture obtained from pollen, produced in the mandibular glands, and a clear, protein-rich secretion from the hypopharyngeal glands. Both glands are located in the head of the nurse bees. Thereafter, the worker larvae receive a mixture of nectar from the honey sac (or honey stomach) and a jelly protein from the hypopharyngeal gland – known as “bee milk.” This glandular – secreted milk is the perfect food for young bees.
In order to produce a queen bee, the larva is continuously fed a secreted jelly substance from both the mandibular and hypopharyngeal glands of the worker bee. This secretion has a higher sugar content and vitamins that are different from the worker food – and is known as royal jelly. When the larva is in the cell and continuously fed substantial amounts of royal jelly, it triggers the development of queen anatomy. When the queen emerges, she will have fully developed ovaries needed to lay eggs as well as a developed spermatheca (undeveloped in worker bees) needed to fertilize eggs. During the queen’s entire life, she is fed large quantities of royal jelly by the nurse bees. This nutritional substance is necessary since the mated queen is laying nearly her body weight in eggs every day during peak colony buildup.
Every beekeeper should understand that the main nutrition of the colony comes from pollen collected from various plant sources by the foraging bees. Pollen provides the necessary nutrients bees need for growth and health such as protein, lipids (fats), minerals, sterols and vitamins. Foraging bees gather between 30 to 100 pounds of pollen each year.
Pollen dearth
Pollen collection by foraging bees is triggered by released brood pheromones and the amount of pollen stored in the hive and the jelly fed to the foragers by nurse bees. Interestingly, brood pheromones are released by the brood and allow the brood to regulate and control the actions of the nurse bees. Sounds backwards, but it’s true: the brood controls the workers. As experienced this Spring, the rain washed away much of the pollen in the plants and the nurse bees were forced to use the vitellogenin stores. Studies have shown that when the protein levels drop, the nurse bees will give preference to feeding the older larvae close to being capped. If the protein levels drop lower, eggs and middle-aged larvae will be cannibalized. The cannibalized brood will be converted into protein.
Fat Bees/Winter Bees
Research has theorized that the Fat Bees or Winter bees evolved as the European honey bees moved into climates of colder weather. It’s the buildup of vitellogenin protein energy reserves that allows the European honey bees to live through the Winter months, or even longer with no pollen resources. The European honey bee has also evolved to store honey which is their carbohydrate energy source. Conversely, the African honey bee, or Africanized honey bees as it’s known in the Americas, strategically search for new food resources rather than storing honey. This lack of storage hinders their progress northward to colder climates.
Because the queen fertilizes eggs to become fat bees and they survive scarce resources, fat bees have been considered a separate caste. The general view of the caste system is a “physically distinct individual or group of individuals specialized to perform certain functions in the colony.” Due to their physical difference with their fat bodies, and because they perform specific functions in the colony during the Winter, they can be considered a separate caste.
Varroa Destructor
For decades, we have believed that the parasitic mite Varroa Destructor consumed the bees hemolymph like a tick consumes blood. Research led by Dr. Samuel Ramsey, Department of Entomology, University of Maryland, determined that varroa actually feed on the vitellogenin in bees’ fat bodies and is their primary source of sustenance, not on the hemolymph. As previously mentioned, vitellogenin molecules are deposited in fat bodies in the head and abdomen of the bees and act as a protein storage reservoir. The varroa will attach itself to the bee in a location to gain the best access to the tissue with the vitellogenin – usually the membrane between segments of the metasoma. To support the idea of varroa accessing the fat bodies is the research that varroa possess attributes associated with feeding on semisolid tissue; they lack essential adaptations associated with hemolymph feeding.
In summary, this magical molecule allows house bees to retain protein in their bodies in the form of vitellogenin. Vitellogenin gives an extra resource to nurse bees and queens allowing them to live longer and make it through periods of limited pollen availability – what specialization!
