How Does Temperature Affect Respiration Rates of Beetles?


Melissa Smith, Bob Schwander, Garth


CU-Boulder, 2006


         In our project we tested the affects of temperature on the respiration rate of Darkling beetles.  Since temperature causes the kinetic energy of enzymes to change, we hypothesized that the temperature inside of the gas chamber would greatly affect the rate of respiration of the Darkling beetle.

         To test this hypothesis we placed 3 Darkling beetles in a gas chamber and attached a carbon dioxide probe.  For each trial we used the same 3 beetles to ensure accurate results.  For the first trial we took 3 Darkling beetles, placed them in the gas chamber and placed 2 high intensity lights above them to warm the chamber to 28 C.  We then measured the levels of CO2 in the chamber for 5 minutes.  After 5 minutes, we let the beetles return back to room temperature.  We then set up an ice bath to cool them to 23 C.  We placed the gas chamber inside the ice bath.  We then collected data for 5 minutes.  We repeated this process a total of 3 times with the same Darkling beetles, so there were data from 3 warm temperature replications and 3 cold temperature replications.  Since temperature causes enzyme activity to slow down, we predicted that the rate of CO2 production would be slower for the Darkling beetles in the cooler environment.

         Our results showed a significant different in the rates of respiration of the Darkling beetles in the warm and cold environments.  This was shown by the T-test that we performed on our data (t=5.05, P < 0.07).  The warm environment had a mean respiration rate of 29.11 ppm/min of CO2.  The cold environment had a mean respiration rate of 17.56 ppm/min of CO2.

         Our results are consistent with our hypothesis.  Nonetheless, we had a few problems that should be addressed in future studies.  We were not able to make all the gas chambers the same temperature for each trial because we were not able to accurately measure the temperature inside the gas chamber.  Also, we had trouble with the beetles.  They seemed to die a few times in the different environments and then come back to life.  Hangge et al. (2001) also showed a significant decrease in the rate of respiration of Darkling beetles in the cold environment.  In the future we would like to explore respiration rates along a gradient of temperatures.