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The Effect of Brood Pheromone on the Longevity and Nutritional Intake of African Honey Bees (Apis mellifera scutellate)
Lake Forest College
Lake Forest, Illinois 60045
Bees mirror the characteristics of an effective worker: loyal, communicative, team-oriented, and hardworking. Bees are known for being industrious workers that work for the collective, and therefore, the good of the hive. These hives are able to function through the use of pheromones, or chemical messages, that they use to communicate with each other. All types of the bees in the hive emit these pheromones, including the larval bees. A pheromone that is particularly important to the survival of these larval bees is the brood pheromone, which plays a part in the feeding of these bees (Démares, Yusuf, Nicolson, & Pirk, 2017). Despite being essential to the early life of these bees, studies have found that brood pheromone can play a part in the premature death of adult bees. In a time where bee populations are on the decline, it is imperative that the number of bees that die decreases as much as possible, in order to help continue pollination that is essential to human life (“Why We Need Bees”, 2011).
Brood pheromone is one of the many important ways for larval bees to communicate to adult bees. This larvae release the pheromone in order to receive food and brood care, which keeps the nutritional needs of the growing insects constant and healthy (Démares, 2017). This is obviously important to the larval bees, as it is how they receive food and care when they need it. Additionally, this emission of brood pheromone also has an effect on the entire hive. In the spring and summer, when brood pheromone levels are high, worker bees begin making more frequent pollen-foraging trips (Démares, 2017). This pheromone also stimulates the development of the bees’ hypopharyngeal glands, which are responsible for protein synthesis and production for the nutrient-rich royal honey that is fed to the larval bees and queen (Smodiš Škerl & Gregorc, 2014). Overall, brood pheromone has a profound effect on not only the health of the larval bees, but also the health of the hive.
This study, conducted by Démares, Yusuf, Nicolson, & Pirk, specifically examined the relationship between the amount of brood pheromone and the amount of food consumed. This study also made a point to examine if there was a relationship between the amount ofbrood pheromone produced and how early these bees died. Additionally, the study looked at how varying levels of brood pheromone affected stimulation of the hypopharyngeal glands, and thus the production of nutrient-rich honey. In this experiment, it was hypothesized that bees exposed to more brood pheromone would respond by eating more protein, both in total and in relative terms. As a consequence, it was predicted there would be a negative effect on survival rate, based on the higher mortality of insects fed on protein-rich diets. The study also hypothesized that bees exposed to brood pheromone would have larger hypopharyngeal glands compared to control bees.
To carry out this experiment, twenty-five African honey bees (Apis mellifera scutellate) were exposed to high levels of brood pheromone, while another twenty-five bees were given a control. Bees were then given a choice between two types of food: food with a 1:30 protein-to-carbohydrate ratio (low amount of protein) and a food source with a 1:3 protein-to-carbohydrate ratio (high amount of protein). This experiment was then recorded for 14 days. After those 14 days, it was first determined that there was little difference in size of the hypopharyngeal glands between bees that were exposed to brood pheromone compared to the control bees. This was done through dissecting ten bees from each group and comparing the size of the glands. They were then electronically depicted, as well as photographed from a microscope, as shown in Figure 1. It was also seen that the bees that were exposed to more brood pheromone had a larger protein intake, as shown in Figure 3a. Additionally, it was seen that the bees that were exposed to higher levels of brood pheromone had a higher overall food consumption, as seen in Figure 3b. This also relates to the discovery that the bees who were exposed to more brood pheromone, who a consumed more protein, had a shorter lifespan, as shown in Figure 2.
Overall, the study discovered that bees that were exposed to higher levels of brood pheromone had a higher intake of protein and food overall. This increased protein intake correlates to a decreased lifespan, as bees that ate more protein died sooner than bees that ate less protein. This experiment also concluded that brood pheromone had no effect on the size of the hypopharyngeal glands. From these conclusions, it can be determined that prolonged exposure to brood pheromone is detrimental to the health of the hive, as it shortens the lifespans of bees, without having any shown benefits, such as creating larger hypopharyngeal glands, which could produce more royal honey (Démares, 2017). In nature, larval bees produce lower levels of brood pheromone after the first couple days of this life stage, so it can be assumed that past this point (around day 3-4), excess protein has a detriment to the bees (Démares, 2017). This information could be used by farmers and beekeepers, as it could allow them to have a tool to stimulate honey production, and thus pollination, when a hive is not pollinating as much. Future studies that could help evaluate how effective brood pheromone is to the productivity of a hive could focus on when and how often brood pheromone is administered, to see if this can increase pollination and productivity, without harming the bees or the hive. In a time where bees have begun to disappear, it is important to look at ways to foster good beekeeping techniques that aid in the longevity and productivity of hives, in order to counter the ill effects of decreasing bee populations.
Démares, F. J., Yusuf, A. A., Nicolson, S. W., & Pirk, C. W. (2017). Effect of Brood Pheromone on Survival and Nutrient Intake of African Honey Bees (Apis mellifera scutellata) under Controlled Conditions. Journal of Chemical Ecology,43(5). doi:10.1007/s10886-017-0840-1
Gregorc, A., & Smodiš Škerl, M. I. (2014, November 25). CHARACTERISTICS OF HYPOPHARYNGEAL GLANDS IN HONEYBEES (Apis mellifera carnica) FROM A NURSE COLONY. Retrieved from file:///C:/Users/natha/Downloads/77-161-1-SM.pdf
Why We Need Bees: Nature’s Tiny Workers Put Food on Our Tables. (2011, March). Retrieved from https://www.nrdc.org/sites/default/files/bees.pdf
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