Protein and the hypopharyngeal gland
Honey bee nutrition is a hot topic these days. Due to their work in monoculture crops, honey bee colonies may not be receiving a well-balanced and complete diet. The surrounding landscape is changing as well, and in many areas, diverse plant life has been replaced by acres of invasive species—another type of monoculture.
Whatever the cause, a poor diet can have devastating results on a honey bee colony. When honey bees lack sufficient pollen or when the pollen is nutritionally incomplete, brood rearing is decreased and worker lifespan reduced. Eventually the colony may collapse.
For bees, pollen is the primary source of the ten amino acids they need to build protein. Most of the pollen is eaten by nurse bees. The nurses use the nutrition absorbed from the pollen to secrete royal jelly from their hypopharyngeal glands. The jelly is fed to young larvae, including workers, drones and queens. After about three days the jelly is mixed with bee bread—a mixture of whole pollen, honey, and enzymes—and fed to the workers and drones until they spin their cocoons. The queens receive a steady diet of royal jelly throughout their larval development.
Some pollen has all the amino acids the honey bees need to raise strong and healthy young bees, but most pollen is deficient in one or more of the necessary amino acids. As a result, it is necessary for honey bees to eat a variety of pollen types, not just one or two.
Researchers at Oregon State University are studying the effects of certain pollen types on the honey bee’s ability to produce protein. The bees are kept in flight cages and fed diets restricted to one type of pollen. A flight cage is a large mesh structure divided into various rooms. Each room houses a hive at one end. The bees can fly in and out of the hive and basically act like normal bees with a single exception—they have access to only one type of pollen.
When the nurse bees reach the age when they begin feeding the brood, the hypopharyngeal gland is removed and tested for its protein content. Although direct analysis of the pollen can reveal the amino acid profile, it cannot determine how well the bee is able to utilize it. An analysis of the protein in the hypopharyngeal gland can reveal just how well the honey bee can use that pollen type and, consequently, can predict the viability of a colony raised on a monoculture of that pollen type.