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Physiology, Biochemistry, and Toxicology

10-Minute Paper

PBT: Physiology On-Demand Presentations

Heat budget model for Centris caesalpiniae male bees in flight

On-Demand
On-Demand
It is advantageous for ecologically important desert pollinators to be functional across a range of temperatures; breadth and success of performance can arise from broad tolerance or thermoregulation. Over the course of two summers (June 2020 and May 2021), we identified potential mechanisms by which the oil-collecting desert bee, Centris caesalpiniae, regulates body segment temperatures. We additionally created a heat budget model to mathematically determine the different avenues of heat gain and loss for C. caesalpiniae in flight. In 2020 and 2021, bees exhibited a slope of thorax temperature on air temperature of 0.37 and 0.24 respectively, indicating better thermoregulation in 2021. Calculations of excess temperature ratio reveal that males moved hemolymph, warmed by the thoracic flight muscles, to the abdomen as air temperature increased in both years. We created a heat budget for hovering, shaded males using measurements of water loss rates and flight metabolic rates and showed that C. caesalpiniae increase both convective and radiative conductance to stabilize thoracic temperatures as air temperature rises. We conclude that C. caesalpiniae thermoregulate high thorax temperatures throughout the morning during flight primarily by varying abdominal surface temperature to control radiative and convective cooling, and that they suspend flight when the difference between thorax and air temperatures reach an average of 8.6 °C. Supported by 2019-2020 Fulbright Student Program and USDA 2017-68004-26322.