The revelation in 2024 that bumblebee matriarchs possessed the astounding capacity to endure prolonged submersion in water for over a week, emerging unharmed, profoundly astonished the scientific community.
Recent scholarly discourse has illuminated the precise mechanisms underlying this remarkable resilience. Central to the bumblebee’s survival repertoire is an extraordinary capability to efficiently extract dissolved oxygen from their aqueous surroundings, effectively granting them the ability to respire underwater for a finite period.
This survival strategy is instrumental in enabling the vital leader of a colony to navigate critical events, such as the inundation of her subterranean dwelling, thereby ensuring her continued existence and facilitating the subsequent reestablishment of her colony once environmental conditions stabilize. Furthermore, its elucidation suggests the potential for certain species to harbor latent reserves of fortitude against formidable environmental adversities.
“Our investigations,” state the research collective, spearheaded by Charles Darveau, an evolutionary physiologist at the University of Ottawa in Canada, “unveil a sophisticated adaptation for flooding resilience and lay the groundwork for a comprehensive examination of the boundaries, physiological processes, and ecological ramifications of aquatic survival in terrestrial arthropods.”
Each year, certain insect populations enter a phase of suspended animation during the winter months, characterized by greatly reduced metabolic activity and developmental processes, a state known as diapause. For numerous bumblebee queens, this involves seeking out secure and sheltered subterranean chambers, settling in, and entering a state of dormancy.
However, these underground sanctuaries are not invariably impervious to environmental disturbances. Subterranean habitats are susceptible to water ingress, and a queen bee in a state of diapause exhibits a level of sluggishness that precludes a rapid response to such an emergent crisis.
Adverse meteorological phenomena, including torrential rainfall, the thaw of snowpack, and rising groundwater levels, can all lead to the submersion of a bee’s domicile. While not a constant threat, these events pose a significant risk, leading to the apparent adaptation observed in at least one North American species, Bombus impatiens.
In 2024, scientific findings demonstrated that queens of the species B. impatiens exhibit an impressive survival rate of approximately 90 percent following up to a week of immersion in water.
The underlying reasons for this remarkable endurance are now coming to light: a synergistic interplay of aquatic respiration, anaerobic metabolic pathways, and a “profound metabolic depression“—an extreme reduction in physiological activity.
Through meticulously controlled laboratory experiments involving numerous queens in winter diapause, researchers subjected the bumblebees to cold water immersion and meticulously documented their metabolic rates and respiratory gas exchanges.
Gas exchange was assessed by analyzing both the water basin containing the immersed insects and the atmospheric environment within the experimental chamber. Analysis of carbon dioxide and oxygen concentrations revealed a marginal increase in the former and a decrease in the latter, indicative of ongoing respiration, suggesting the bees were indeed extracting oxygen from the water and releasing carbon dioxide.
Concurrently, observations of submerged individuals revealed an accumulation of lactate. This occurs when the organism’s oxygen supply is insufficient, prompting cells to engage in an alternative metabolic process that generates energy in the absence of oxygen. Lactate represents a metabolic byproduct of this anaerobic respiration.
Furthermore, the bees’ metabolic processes are drastically curtailed to the absolute minimum necessary for sustaining life. Diapause itself already diminishes a queen’s metabolic rate by upwards of 95 percent. Submersion further exacerbates this reduction. By employing carbon dioxide production as an indicator of metabolic activity, the magnitude of this decline becomes evident.
Prior to submersion, diapausing queens exhibited a carbon dioxide output of approximately 15.42 microliters per hour per gram of body mass. Following an eight-day period underwater, this production rate diminished to 2.35 microliters, representing roughly one-sixth of its initial level.
Collectively, these physiological adaptations empower the queens to absorb oxygen directly from their aquatic environment while simultaneously minimizing their energy expenditure to an extraordinary degree.
While this constitutes an exceptionally elegant survival mechanism, certain aspects remain enigmatic. The precise mechanism by which B. impatiens achieves oxygen extraction from water has not yet been definitively elucidated. Researchers hypothesize that the queens may utilize a physical gill—a thin layer of entrapped air facilitating gas exchange with the water—though this remains to be empirically verified.
Further research is warranted to delineate the definitive limits of this remarkable survival capacity.
“Subsequent investigations involving the manipulation of aquatic conditions and the putative physical gill, coupled with in-depth analyses of recovery processes, will further elucidate the adaptive strategies that enable queens to withstand prolonged periods of submersion,” the authors conclude.
