Project Overview
Annual Reports
Commodities
- Animals: bees
Practices
- Animal Production: general animal production
- Education and Training: demonstration, extension, technical assistance
- Pest Management: economic threshold, genetic resistance
- Production Systems: holistic management
- Sustainable Communities: sustainability measures
Abstract:
Honey bees are the major providers of pollination services for cultivated and native flowering plants. The output derived predominantly from honey bee pollination ensures a diverse and nutrient-rich food source for human and animal consumption, as well as provides billions of dollars in domestic and global revenue. The condition of the pollinating capacity and overall health of honey bees in the U.S. has eroded in recent years. Beekeepers have bared the brunt of this health crisis through heavy annual losses of their colonies starting in 2006. Contributing to these losses are mite pests, pathogens, pesticides, and nutritional deficiencies that can interact and jeopardize honey bee colony productivity and survival. One pathogen, Nosema ceranae, has caused reason for concern as it is often found at high levels in both healthy and dying colonies.
An age-based division of labor maintains social organization in honey bee colonies, such that young bees tend to remain in the nest as nurse bees, feeding larvae and the queen, and older bees tend to forage for nectar and pollen outside the nest. Many factors such as the environment, nutrition, or pathogens may act on honey bee physiology to disrupt the timing of the transition from nursing to foraging. This research used cage and field studies to examine the effects of N. ceranae infection on levels of vitellogenin and juvenile hormone, endocrine signaling factors that are fundamental to regulating foraging onset and lifespan in honey bees.
Introduction:
Many beekeepers are finding that it is increasingly difficult to keep their honey bee colonies alive. Exposure to mite pests, pathogens, pesticides, and nutritional deficiencies create a ‘perfect storm’ of factors that can interact and jeopardize colony productivity and survival. The outcome of this health crisis has been losses of nearly one-third of U.S. honey bee colonies annually. Our current rate of colony death is unsustainable and will ultimately result in fewer bees available to pollinate the fruits, vegetables, and native plants that we and other animals depend on for food and shelter.
No one factor can be singled out as an explanation for widespread colony losses; however, the emerging pathogen, Nosema ceranae, has caused reason for concern as it is often found at high levels in both healthy and dying colonies. N. ceranae is a spore-forming fungus that infects and reproduces inside an adult bee’s gut. When a bee ingests N. ceranae spores, they germinate and undergo reproduction inside cells that line the area of the bee gut where food is absorbed. N. ceranae may limit an infected bee’s access to nutrients as the bee and fungus compete for resources, ultimately shortening a bee’s lifespan. During the course of infection, millions of spores are produced and released back into the environment when the bee defecates. These spores serve as a source of infection for other bees. For a honey bee colony that contains tens of thousands of workers, infection and premature death of one bee would be an insignificant loss; however, as infection spreads to a large number of bees a cascade effect can ensue as the foraging population dies and the queen is not able to lay enough eggs to keep up with the loss.
There are gaps in our understanding of how N. ceranae may cause colony death. This research focuses on finding answers to the following fundamental questions to help fill some of these gaps: How does infection by N. ceranae affect bee behavior? What is the underlying physiological mechanism responsible for these behavioral changes?
A honey bee colony is a family comprised of a queen mother, up to 40,000 daughters (workers) and a small percentage of sons (drones). Workers typically live 6 weeks during the summer. Young workers remain in the nest as nurses, feeding the larvae and queen, and at about 3 weeks of age the workers switch from nursing duties to foraging for nectar and pollen outside the nest for their remaining 2-3 weeks of life. Underlying this age-based division of labor is a protein called vitellogenin (Vg) and juvenile hormone (JH). Nurse bees have high levels of Vg and low levels of JH, whereas at the onset of foraging, they have low levels of Vg and high levels of JH. The interaction of Vg and JH functions as a pacemaker that drives the sequence of behaviors that workers perform throughout their lives. Factors such as the environment or pathogens may act on honey bee physiology to disrupt this developmental pacemaker.
N. ceranae could provide a mechanism that promotes premature and pathological onset of foraging in workers, ultimately leading to a shortened life span at the individual level and an absence of adult bees at the colony level. Moreover, N. ceranae infection could exert behavioral effects on its host through disruption of Vg/JH endocrine signaling.
Project objectives:
Objective 1. Determine the life span and identify the onset of foraging behavior in newly emerged worker bees infected with N. ceranae.
Objective 2. Determine how N. ceranae infection affects expression of vitellogenin and juvenile hormone, which are physiological regulators of adult development in honey bees.