Respiration Rates of Crickets: A light atmosphere compared with a dark atmosphere

Kristina Martin and Kathryn Knapp

CU Boulder, Fall 2002

We tested the rates of respiration of crickets in two different atmospheres, a lighted atmosphere, and a dark atmosphere. The question we were searching to answer was whether or not crickets are nocturnal. We hypothesized that crickets are indeed nocturnal animals, since they are always heard chirping in the nighttime. If crickets are nocturnal, then we predicted that they would respire faster in a dark atmosphere than in a light atmosphere, as measured by an increased rate of CO2 change, because they are more comfortable and more active in the dark.

We measured about two grams of crickets and put them into a beaker exposed to the light. Then we used the CO2 sensor and the Logger Pro "respiration" program from the lab manual CD-ROM. We evaluated the CO2 production of the crickets in the beaker for five minutes. Next, we covered the beaker with foil and allowed the crickets to settle for two minutes into a dark atmosphere and ran the respiration program again. We ran the three trials with different crickets used in each test. Once we obtained the data, we were able to show the change in CO2 production (a measure of respiration rate) inside the beaker per minute per gram of crickets for both the light and dark atmospheres. For each trial on crickets, we also ran a trial on an empty beaker to eliminate the possibility of any CO2 change coming from the beaker itself.

To analyze the data we ran a t-test on the obtained values and found that respiration rates were significantly higher (P = .049) in a light atmosphere (mean = 51.42 ppm CO2/min/g) than in a dark atmosphere (mean = 27.68 ppm CO2/min/g). Our results are inconsistent with our predictions. The great potential source of error in our experimental design lies in the fact that the crickets used in lab experiments are kept in a glass bottle and left in the light for long periods of time. These particular crickets have had time to adapt, and possibly to become more comfortable in a lighted atmosphere. More accurate results could have been obtained from crickets taken from a natural environment and kept in surroundings with a similar day/night cycle. On www.cricketscience.com, in the "Frequently Asked Questions" section, we asked whether or not crickets are nocturnal. The website answers that crickets are nocturnal by nature, but that this quality is "more likely facultative that obligatory," meaning that although crickets are nocturnal by nature, this state is not definitive. When left in light crickets can adapt to the new atmosphere. This fact from www.cricketscience.com allows us to look at our results in a different light. The crickets in the lab are more comfortable and active in the light because they are in the light at most times. Still, the hypothesis cannot be rejected, because no trial was run on crickets from a natural atmosphere. A future experiment could test the statement from www.cricketscience.com by running a similar experiment to ours on crickets from a natural atmosphere compared to crickets raised in a light atmosphere. It is also highly possible that crickets run a circadian rhythm, and a more inclusive experiment would encompass testing crickets at different times of day as well. Including both types of crickets and varying the times at which the trials are run would offer more definitive results on the natural activity rates of crickets.