A new study by entomologists at the University of Maryland shows that the lifespan of individual honeybees kept in a controlled, laboratory environment is 50% shorter than it was in the 1970s. When scientists modeled the effects of today’s shorter lifespans, the results matched the trends of increased colony loss and decreased honey production seen by US beekeepers in recent decades.
Colony turnover is an accepted factor in the beekeeping business because bee colonies naturally age and die. But in the past decade, U.S. beekeepers have reported high loss rates, which have meant replacing more colonies to keep operations sustainable. To understand why, researchers have focused on environmental stressors, disease, parasites, pesticide exposure, and nutrition.
This is the first study to show an overall reduction in honey bee lifespan, potentially independent of environmental stressors, and suggests that genetics may influence broader trends observed in the beekeeping industry. The study was published on November 14, 2022 in the journal Scientific Reports.
“We isolate bees from colony life before they reach adulthood, so anything that shortens their lifespan is happening by then,” said Anthony Nearman, Ph.D. He is a student of the Department of Entomology and the lead author of the study. “This introduces the idea of a genetic component. If this hypothesis is correct, it also points to a possible solution. If we can isolate some genetic factors, then perhaps we can breed longer-lived honey bees.”
Nearman first noticed the reduction in lifespan while researching standardized protocols for rearing adult bees in the laboratory with Dennis van Engelsdorp, associate professor of entomology. Replicating previous research, the researchers collected bee pupae from honey bee hives within 24 hours of the pupae emerging from the wax cells in which they grew. The collected bees completed their growth in an incubator and were then kept in special cages as adults.
When Nearman evaluated the effect of supplementing the sugar water diet of caged bees with plain water to better mimic natural conditions, he noticed that the average lifespan of his caged bees, regardless of diet, was half that of caged bees in similar experiments in the 1970s. . (17.7 days today versus 34.3 days in the 1970s.) This prompted a deeper review of laboratory studies published over the past 50 years.
“When I plotted the lifespan over time, I realized, wow, there’s actually this big time effect going on,” Nearman said. “Standardized protocols for rearing honeybees in the lab weren’t really formalized until the 2000s, so you’d think that lifespans would be longer or the same because we’re getting better at it, right? Instead, we’ve seen the mortality rate double. “
Although the laboratory environment is very different from the colony, historical records of bees kept in the laboratory show that colony bees have similar lifespans, and scientists generally assume that isolated factors that reduce lifespan in one environment will also reduce it in another. Previous research has also shown that in the real world, shorter honey bee lifespans correspond to less foraging time and less honey production. This is the first study to link those factors to colony turnover rates.
When the team modeled the effect of a 50% reduction in lifespan in a beekeeping operation where lost colonies were replaced annually, the resulting loss rates were about 33%. This is very similar to the average overwintering and annual loss rates of 30% and 40% reported by beekeepers over the past 14 years.
Nearman and vanEngelsdorp noted that their laboratory-kept bees may have been exposed to some sort of low-level viral contamination or pesticide while they were being laid in the hive and worker bees were feeding them in the larval stage. But bees showed no obvious signs of these exposures, and a genetic component to longevity has been shown in other insects, such as fruit flies.
The next steps for the researchers will be to compare honey bee lifespan trends in the United States and other countries. If they find differences in longevity, they can isolate and compare potential contributing factors, such as genetics, pesticide use, and the presence of viruses in local bee populations.
Provided by Materials University of Maryland. Originally written by Kimbra Cutlip. Note: Content may be edited for style and length.