Nocturnal Respiration

Alison Beardsley and Paige Claassen

Why do nocturnal organisms sleep during light hours and become active during dark hours? Some crickets, for example, have evolved to have a better chance of survival during the night rather than during the day due to natural selection; therefore we can say that crickets are more active at night. Since the cellular respiration level of crickets becomes higher as the cricket becomes more active, we hypothesized that nocturnal organisms are biologically adapted to have higher respiration rates at night than during the day.

            To test our hypothesis, we obtained five crickets and placed them in a plastic gas chamber with a CO2 concentration probe. We placed a lit desk lamp on the gas chamber for five minutes, with a container of water in between to absorb the heat, and measured the amount of CO2. For simulation of night we covered the chamber completely in aluminum foil and collected the data for another five minutes. We ran four separate trials with different crickets with the same two treatments. Since crickets are nocturnal and therefore more active at night, we predicted that the respiration rates would be higher with the aluminum foil than without the foil.

            Our results show that the cellular respiration of the crickets was higher in the light [mean=0.883 (ppm/sec) (1/g)] than in the dark [mean=.667 (ppm/sec) (1/g)], and the light conditions did not have a significant influence on the cellular respiration of crickets (P=0.0587).

            We found that our results are inconsistent with our hypothesis, and cannot provide any substantial support for our predictions. One possible problem with our experimental design has to do with the accuracy of the environment representing light hours and dark hours. For instance, light is not the only factor that distinguishes night and day. You also have to take other factors such as climate change and predators into consideration. Another potential problem with our experimental design was that we did not give each treatment enough time to accurately depict the circadian rhythm of the crickets. Instead of five minutes for each trial, we needed to make each trial twenty-four hours long, with twelve hours for each treatment to represent night and day more accurately. Based on our results, we propose an alternative hypothesis. Maybe nocturnal animals sleep during the day not because they are biologically adapted to have a higher cellular respiration rate, but because their biological clocks are adjusted to factors such as predators, prey, or senses. For example, studies on nocturnal animals done by Sharma et al. (2003) suggests that “circadian clocks” are found in organisms ranging from bacteria to mammals, and that these organisms have an intrinsic adaptive value to its environment. Perhaps crickets are adapted to stay awake at night due to environmental factors rather than internal factors.



Sharma, Vijay Kumar(2003)'Adaptive Significance of Circadian Clocks',Chronobiology International,20:6,901 — 919