The lifespan of honey-producing bees kept in a controlled laboratory environment is 50% shorter today than it was 50 years ago, according to a study by entomologists at the University of Maryland in the US.
When scientists modeled the effect of today’s shorter lifespans, the results matched the trends of increased colony losses and reduced honey production seen by American beekeepers in recent decades.
Colony turnover is an accepted factor in beekeeping, as bee colonies naturally age and die. But over the past decade, beekeepers in the U.S. have reported heavy losses, leading to the replacement of several colonies to continue operations. In an attempt to understand what happened, researchers focused on environmental stressors, disease, parasites, pesticide exposure and nutrition.
The decrease in the lifespan of bees, explained by genetic factors
This is the first study to show a general decline in the lifespan of honey bees, potentially independent of environmental stressors. The study suggests that genetics could influence broader trends seen in the beekeeping industry.
“We isolate bees from colony life just before they emerge as adults, so anything that shortens their lifespan happens before that point. This introduces the idea of a genetic component. If this hypothesis is correct, it also points to a possible solution. If we can isolate certain genetic factors, then maybe we can breed them so that we get longer-lived bees,” said Anthony Nearman, PhD student in the Department of Entomology and lead author of studied.
How did the analysis of laboratory bees begin?
Nearman first noticed the decline in lifespan while conducting a study with Associate Professor of Entomology Dennis van Engelsdorp on standardized protocols for rearing adult bees in the laboratory.
Nearman was evaluating the effect of supplementing the sugar water diet of bees in plain water cages to better mimic natural conditions when he noticed that, regardless of diet, the average lifespan of bees in his cages was half that of caged bees from similar experiments in the 1970s.
“When I plotted the lifespan over time, I realized that there is actually this huge effect. Standardized protocols for raising bees in the lab weren’t really formalized until the 2000s, so you’d think the lifespan would be longer or unchanged because we’re getting better at it, right? Instead, we saw a doubling of the death rate,” Nearman said.
What’s next to pinpoint the cause of the bee’s declining lifespan?
Although a laboratory is a different environment than a colony, historical records of bees kept in the laboratory suggest a lifespan similar to that of colony bees, and scientists generally assume that isolated factors that reduce lifespan in in one environment they will reduce it in another as well Phys.org.
Nearman and van Engelsdorp noted that bees kept in the lab could be subject to some sort of low-level viral contamination or pesticide exposure during their larval stage, when they hatch in the hive and are fed by worker bees. But the bees showed no obvious symptoms of these exposures.
The next steps will be to compare trends in honey bee lifespans in the US and other countries. If they find differences in longevity, researchers can isolate and compare potential contributing factors, such as genetics, pesticide use, and the presence of viruses in local bee stocks.