Fluctuations in oxygen influence facultative endothermy in bumblebees

Area of Science:

• Zoology
• Insect Physiology
• Environmental Biology

Background:

• Bumblebees are facultative endotherms, capable of regulating their thoracic temperature.
• Endothermy is crucial for bumblebee activity, especially in cooler environments.

Purpose of the Study:

• To investigate the effects of hypoxia on the metabolic demands and thermoregulatory abilities of Bombus terrestris.
• To determine the critical oxygen levels affecting bumblebee endothermy.

Main Methods:

• Measuring thoracic temperature, oxygen consumption, carbon dioxide production, and abdominal pumping rates.
• Exposing bumblebees (Bombus terrestris) to varying oxygen levels (20, 15, 10, and 5 kPa) at a constant ambient temperature (26°C).

Main Results:

• Bumblebees maintained a mean thoracic temperature of 35.5°C under normoxia.
• Thoracic temperature remained stable at 15 kPa O2 but decreased significantly at 10 kPa O2 and 5 kPa O2.
• Metabolic rate and abdominal pumping were maintained at 15 kPa O2 and partially at 10 kPa O2, but compromised at 5 kPa O2.

Conclusions:

• Bumblebees can sustain endothermy under moderate hypoxia (15 kPa O2).
• Severe hypoxia (10 kPa O2 and below) significantly impairs bumblebee thermoregulation and metabolic function.
• These findings highlight the sensitivity of insect endothermy to oxygen availability.