When people talk about animals capable of holding their breath for long periods, marine mammals usually come to mind. Yet a recent discovery suggests that a terrestrial insect may also have surprising talents: the bumblebee queen.
Researchers have shown that some bumblebee queens can survive several days completely submerged in water, sometimes up to a week. An unexpected feat for an insect that spends most of its life… in the air.
An Observation Born from a Laboratory Accident Involving Bumblebee Queens
The discovery stemmed from experiments on Bombus impatiens, a North American bumble bee species that has been extensively studied. Scientists were working with queens in diapause, the hibernation phase that follows mating in late autumn, according to Science News(1). During a manipulation, water infiltrated tubes containing the queens. Assuming the insects were dead, researchers were surprised to find that a large portion would awaken normally after immersion.
To verify this phenomenon, they carried out a series of controlled experiments on more than a hundred queens:
- immersion of 8 hours to 7 days
- water kept at a stable temperature
- comparison with a non-immersed control group
Result: about 80% of queens survived after a week underwater, a rate close to that of the control group. The immersion thus does not increase mortality among bumble bee queens.
Minimal but Real Respiration
Scientists then measured gas exchange during immersion. Even underwater, the queens still produced carbon dioxide (CO₂), a sign that their metabolism was not completely halted. At the same time, the concentration of dissolved oxygen in the water decreased slightly. These observations suggest that oxygen may diffuse slowly into the insect’s respiratory system.
Insects don’t breathe through lungs but through a network of tubes called the tracheal system. Air enters through small lateral openings: the spiracles. Oxygen then diffuses directly to the tissues. Even when submerged, these structures can allow a slow diffusion of dissolved oxygen in water, especially if metabolic activity is very low.
The Key Role of Diapause
Survival underwater would likely be impossible without the winter diapause. In bumble bee queens, this phase triggers major physiological changes: a drastic reduction in metabolism, buildup of lipid reserves, increased tolerance to environmental stress, and a slowdown of respiration.
In the study, researchers observed a dramatic drop in metabolic activity. CO₂ production fell from about 15 µL per hour per gram of body weight to about 2 µL after several days of immersion.
When oxygen becomes scarce, cells can generate energy without oxygen through anaerobic glycolysis. This mechanism produces lactate, a compound also seen in animals deprived of oxygen for a period. Analyses showed an increase in lactate in the tissues, indicating that queens temporarily rely on this metabolic pathway to survive when oxygen becomes insufficient.
An Adaptation to a Bumble Bee’s Subterranean Life
This ability could be explained by the very particular ecology of bumble bee queens.
After mating, in late summer or autumn, the future queen burrows into the soil, enters diapause for several months, and emerges in the spring to found a new colony.
During this underground winter, the burrow can be flooded by rain or melting snow. Immersion tolerance could therefore be an evolutionary adaptation allowing the queen—and thus the entire future colony—to survive these episodes.
- https://www.sciencenews.org/article/hibernating-bumblebee-queen-underwater
