October 26, 2016
Contrary to popular belief, proteins in larval foods of honeybees do not determine the larvae’s growth into queen bees. This includes the protein royalactin, which was previously thought to be the “queen determinate” since 2011. This is the finding of a study from the Martin Luther University Halle-Wittenburg, which was published in the journal Nature.
In the days after hatching, honeybee larvae feast on the royal jelly that is secreted out of the hypopharyngeal glands of adult bees. “It is a highly nutritious food comprising of sugars, proteins, and amino acids,” Robin Moritz, a professor of Molecular Ecology at MLU, said. After several days, larvae start receiving honey and pollen in their food. Almost all grow into worker bees, but only the bees meant to become queens continue to feed on royal jelly. The surviving queen, as the only sexually reproductive female, is in charge of the production of offspring in the colony.
“Scientists have spent a long time looking for a specific substance in royal jelly that makes the larvae grow into queens,” says Dr. Anja Buttstedt, a research associate of Moritz’s and an author of the study. In the 1970s, a German biochemist, Heinz Rembold, already concluded no single substance determined a queen---a right mix of essential nutrients did instead.
“The special royal diet makes the larvae eat more, stimulating their metabolism and the larval developments inside the bees’ bodies,” Buttstedt claims. The royal diet is also required in order to develop functioning ovaries, as opposed to the sterile female worker bees. This was the consensus for many decades. In 2011, however, a Japanese scientist, Masaki Kamakura, caused a stir when he published a study in which he presented the protein royalactin as the determinant that turned larvae into queens.
So, this recent study’s biologists decided to recreate Kamakura’s experiments. They followed his approach by producing a jelly containing no royalactin and feeding it to larvae in a lab. The control group received the same food artificially enriched with royalactin. Buttstedt said, “Neither the royalactin-free nor the enriched larval food produced any difference in the queen caste determination.”
The non-royalactin fed bees turned into perfect queens while the other did not increase the number of queens. Unlike Kamakura’s study, the MLU experiment rendered queens called intercastes---bees who are both workers and queens. This experiment confirms older studies, not Kamakura’s. For now, royalactin’s role remains just another protein source in larval food.