Changes in respiratory structure and function during post-diapause development in the alfalfa leafcutting bee,...

Area of Science:

• Insect physiology
• Developmental biology
• Environmental adaptation

Background:

• Megachile rotundata, the alfalfa leafcutting bee, is a solitary, cavity-nesting insect.
• Developing bees may experience hypoxic conditions due to their brood cell structure and nesting environment.
• Understanding hypoxia tolerance is crucial for pollinator health.

Purpose of the Study:

• To test the hypothesis that M. rotundata are adapted to hypoxic conditions.
• To measure the critical oxygen level (Pcrit) for developing pupal bees.
• To investigate developmental changes in tracheal structure and their relation to hypoxia tolerance.

Main Methods:

• Flow-through respirometry was used to measure CO2 emission rates across a range of oxygen partial pressures (PO2).
• Critical PO2 (Pcrit) was statistically determined for pupal M. rotundata of varying ages.
• Synchrotron X-ray imaging was employed to analyze tracheal diameters during development.

Main Results:

• The mean Pcrit for M. rotundata was 4 kPa PO2, with a range of 0-10 kPa, indicating significant hypoxia tolerance.
• Pcrit was positively correlated with age, suggesting decreased tolerance to hypoxia as pupae mature.
• Tracheal diameters increased with age but varied by location, potentially explaining shifts in hypoxia tolerance.

Conclusions:

• Developing M. rotundata exhibit substantial hypoxia tolerance, with Pcrit values comparable to other insects.
• Changes in tracheal structure during metamorphosis influence hypoxia tolerance.
• This study provides novel insights into the respiratory physiology of developing bees, essential for pollinator conservation.