Bumblebee Queens Demonstrate Underwater Respiration and Metabolism Reduction for Survival

Bumblebee Queens Reveal Remarkable Underwater Survival Strategy

In 2024, scientists unveiled an astonishing discovery: bumblebee queens possess the ability to survive over a week submerged in water. A new study now details the intricate mechanisms behind this resilience, including a unique capacity to extract oxygen from water, enabling temporary underwater respiration. This extraordinary ability equips queens to withstand critical events like flooded burrows and highlights the inherent resilience some species hold against environmental extremes.

"The findings reveal a flooding-tolerance strategy and provide a basis for further study into underwater survival in terrestrial insects."
— Charles Darveau, Evolutionary Physiologist, University of Ottawa

Many insect species, including bumblebee queens, navigate winter through diapause – a state of suspended development and metabolism. Queens typically enter this hibernation-like state within underground burrows. However, these subterranean shelters are highly susceptible to flooding from unpredictable weather events, such as heavy rain, snowmelt, and rising water tables. Bumblebees in diapause have significantly reduced mobility, severely limiting their capacity to respond to such emergencies.

The North American species Bombus impatiens has notably demonstrated adaptation to these challenging conditions. Previous research earlier in 2024 indicated that B. impatiens queens exhibited a survival rate of approximately 90 percent after up to a week of water submersion.

The current study pinpoints the sophisticated survival mechanisms at play during submersion:

• Underwater respiration
• Anaerobic metabolism
• Profound metabolic depression (an extremely minimal metabolic state)

In controlled laboratory experiments, researchers submerged dozens of winter-diapausing queens in cold water, carefully monitoring their metabolism and gas exchange. Measurements of gas exchange were taken both in the water surrounding the bees and in the air above it. Monitoring carbon dioxide and oxygen levels revealed a slight increase in carbon dioxide and a decrease in oxygen, consistent with respiration where bees absorb oxygen from the water and release carbon dioxide.

Submerged bees also showed significant lactate accumulation, a clear indicator of a shift to anaerobic metabolism. This process generates energy without oxygen, producing lactate as a byproduct. Furthermore, their metabolism was drastically reduced to the absolute minimum necessary for survival. While diapause itself decreases a queen's metabolism by over 95 percent, submersion reduces it even further. Carbon dioxide production, used as a proxy for metabolism, strikingly illustrated this reduction. Prior to submersion, diapausing bees produced approximately 15.42 microliters of carbon dioxide per hour per gram of body mass. After eight days submerged, this rate plummeted to 2.35 microliters, representing about one-sixth of the initial value.

These combined processes enable the queens to absorb oxygen from the water while maintaining extremely low energy requirements. However, the exact method by which B. impatiens queens extract oxygen from water remains undetermined. Researchers hypothesize that the queens may utilize a physical gill—a thin layer of trapped air that facilitates gas exchange with the surrounding water—but this intriguing possibility requires further confirmation.

Further research is critical to establish the precise limitations of this remarkable survival capability. The research team indicated that future studies involving the manipulation of water conditions, investigation of the potential physical gill, and comprehensive recovery analyses would provide deeper insights into the adaptations that allow these queens to endure prolonged submersion.

The research findings were published in the esteemed journal Proceedings of the Royal Society B: Biological Sciences.