Heat exposure limits pentose phosphate pathway activity in bumblebees

Area of Science:

• Ecology
• Physiology
• Climate Change Biology

Background:

• Bumblebee populations are declining globally due to climate change, impacting essential pollination services.
• Bombus impatiens, an economically important bumblebee species, faces threats from extreme heat events.
• The pentose phosphate pathway (PPP) is crucial for generating antioxidant potential via nectar sugars.

Purpose of the Study:

• To investigate the physiological mechanisms underlying Bombus impatiens susceptibility to extreme heat.
• To test if heat exposure limits the activity of the pentose phosphate pathway (PPP).

Main Methods:

• Tracking PPP activity in Bombus impatiens using isotopically labeled glucose at rest, during exercise, and recovery.
• Comparing PPP activity under moderate (22°C) and high (32°C) temperature regimes.
• Assessing oxidative damage and antioxidant potential (GSH:GSSG ratio) after heat exposure.

Main Results:

• PPP activity was reduced in Bombus impatiens during high ATP demand (exercise) and heat exposure.
• Bees exposed to 32°C showed a lower GSH:GSSG ratio, indicating reduced antioxidant potential.
• Minimal oxidative damage was observed, but antioxidant capacity was compromised under heat stress.

Conclusions:

• Acute heat stress significantly limits PPP activity and antioxidant potential in Bombus impatiens.
• Repeated heat stress may have severe physiological consequences for this species.
• The findings suggest potential negative implications for North American pollination services.