Ecologist Sabrina Rondeau made an accidental discovery: queen bees possess the ability to remain submerged underwater without drowning. During the winter of 2022, while pursuing her doctoral studies at the University of Guelph, she noticed that condensation dripping from a fogged-up refrigerator was falling into containers holding four queen bees in hibernation. Upon retrieving them, she was amazed to find them still alive. Now, she and her colleagues have uncovered the mechanism enabling the bees to accomplish this feat without needing to hold their breath.
The research findings, published in the Proceedings of the Royal Society, enhance our comprehension of bumblebee remarkable capabilities.
In 2023, Rondeau began a postdoctoral position in the Biology Department at the University of Ottawa. There, she connected with evolutionary physiologist Charles Darveau. It turned out that both shared an interest in diapause—a quasi-hibernation state bumblebee queens enter to survive the winter.
Darveau calculated that if the bees simply stopped breathing by sealing the openings of their tracheal tubes (which deliver oxygen to tissues), their stored oxygen supply would deplete in mere hours. Therefore, during overwintering, the insects likely slow their metabolism even further—more significantly than during regular diapause—resulting in a much lower oxygen demand.
It is possible they also partially switch to anaerobic metabolism, a method of energy generation that doesn’t require oxygen. This process is typically observed in microbes but can be utilized by animals, such as in muscles during brief bursts of activity. However, anaerobic metabolism has a drawback: it leads to the accumulation of lactate, a potentially harmful byproduct.
Not a single bumblebee drowned during the water experiment. Photo: Charles Darveau
Darveau, Rondeau, and student Skyelar Rojas examined 50 bumblebee queens kept in diapause within a refrigerator. The insects were placed individually into small containers almost entirely filled with water. Over an eight-day period, the scientists measured the amount of carbon dioxide ($\text{CO}_2$) emitted by the submerged bees.
Compared to bees in diapause maintained in air, the submerged insects released 75% less $\text{CO}_2$ on the first day. This indicates that their metabolic rate dropped by over half.
Subsequently, their metabolism continued to slow down gradually, further reducing the bees’ oxygen requirements. Additionally, the insects partially transitioned to anaerobic metabolism—energy production without oxygen. This was evidenced by a fifteen-fold increase in lactate concentration within their bodies.
Darveau theorizes that bumblebees might still manage to obtain a small amount of oxygen even when underwater. This is likely facilitated by a thin layer of air retained on the surface of their bodies. This layer of air, known as a “physical gill,” is employed by various aquatic insects; it allows oxygen and carbon dioxide to exchange with the surrounding water.
The researcher observed the bumblebees gradually recover over several days after being removed from the water-filled vials.
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