Bumblebee Queens Survive Prolonged Submersion, Challenging Insect Physiology

In a remarkable discovery that redefines our understanding of insect resilience, researchers have found that bumblebee queens can survive for up to a week underwater. The finding, published March 10 in Proceedings of the Royal Society B: Biological Sciences, reveals a previously unknown ability to breathe underwater and switch to an anaerobic metabolism, raising questions about how these vital pollinators cope with increasingly frequent flooding events linked to climate change.

The initial observation came about almost by accident. Biologist Sabrina Rondeau, along with colleagues at the University of Ottawa, noticed that hibernating eastern bumblebee queens (Bombus impatiens) didn’t drown when vials holding the queens flooded in a lab setting. This unexpected survival sparked a deeper investigation led by ecological physiologist Charles Darveau and his team.

How Do They Do It? A Metabolic Shift

Darveau initially calculated that the amount of oxygen a bumblebee queen would demand to survive for a week underwater was impossible given their size – roughly one milliliter in volume. “One bumblebee queen roughly one milliliter in volume would need 20 milliliters of oxygen,” he explained. “So, it was impossible.” The team then conducted a controlled experiment, submerging hibernating queens in vials of cold water for eight days. Their measurements revealed that the queens weren’t simply holding their breath.

Instead, the bumblebee queens were actively breathing underwater, continuously releasing carbon dioxide. Crucially, the researchers also found a significant increase in lactic acid levels within the bees’ bodies, indicating a switch to anaerobic metabolism – a process that allows organisms to produce energy without oxygen. This metabolic slowdown, already present during hibernation to conserve energy, appears to be key to their underwater survival. Science News provides further detail on this process.

Hibernation and Flood Risk: A Vulnerable Period

Bumblebee queens spend the winter months hibernating underground, digging nests where they are vulnerable to flooding. This discovery is particularly relevant given the increasing frequency and intensity of heavy rainfall events associated with climate change. The ability to withstand submersion is a crucial adaptation, but the extent of that resilience remains an open question.

Darveau and his team are now investigating how repeated or prolonged submersion might impact the queens’ energy reserves. Hibernation is an energetically demanding period, and repeated dips underwater could deplete vital resources, potentially impacting their ability to successfully establish new colonies in the spring. “There might be some point of no return,” Darveau cautions.

Anaerobic Metabolism Explained

Anaerobic metabolism is a process that allows cells to generate energy without using oxygen. While less efficient than aerobic metabolism (which uses oxygen), it provides a temporary energy source when oxygen is limited or unavailable. A byproduct of anaerobic metabolism is lactic acid, which can build up in muscles and tissues, leading to fatigue. The observed increase in lactic acid levels in the submerged bumblebee queens confirms that they were relying on this alternative energy pathway.

What Remains Unclear

While the study demonstrates that bumblebee queens can survive prolonged submersion, the exact mechanisms allowing them to “breathe” underwater are still unknown. Researchers speculate that, like many aquatic insects, the queens may trap a thin layer of air around their bodies, allowing for gas exchange. Further research is needed to confirm this hypothesis and to fully understand the physiological processes involved. The Royal Society Publishing details the study’s methodology and findings.

Implications for Conservation

Bumblebees are essential pollinators, playing a critical role in both agricultural ecosystems and natural environments. Declining bumblebee populations are a growing concern, and understanding their resilience to environmental stressors like flooding is crucial for effective conservation efforts. This research highlights the importance of protecting and restoring bumblebee habitats, particularly those prone to flooding. Charles Darveau’s faculty page at the University of Ottawa provides information on his broader research interests in insect physiology and energetics.

The team’s next steps involve investigating the limits of this underwater survival capability. How many submersion events can a queen withstand before it impacts her reproductive success? What are the optimal water temperatures for survival? Answering these questions will be vital for predicting the long-term effects of climate change on bumblebee populations.