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The effect of temperature on metabolic rates of a domestic mouse and southern leopard frog
Lab Report 1
Spring Semester 2013
by
Caleb Knight
For
Principles of Zoology II Lab
Thursday, 3:30
Instructor: Meyers
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Introduction
Temperature has an affect on many aspects of the life of an animal. One of the affects
that temperature has on animals is on physiology, particularly the metabolic rate. Temperature
affects the metabolic rate of ectotherms (Killen et al., 2010) and endotherms (Clark et al., 2010)
differently.
In this study I tested how temperature affects ectotherms and endotherms differently.
The endotherm I used was the domestic mouse (Mus musculus) and the ectotherm I used was the
southern leopard frog (Lithobates sphenocephalus). Based on prior research I predict that as
temperature decreases the metabolic rate of the mouse will increase and the metabolic rate of the
frog will decrease.
Materials and Methods
I used a makeshift volumeter (Fig. 1) consisting of a flask with a small amount of soda
lime and cotton, as well as a rubber stopper, tubing and a pipette to measure the oxygen used by
the mouse. To determine the weight of the mouse I weighed the the flask before and after placing
the mouse inside. Once the mouse was placed inside, I measured and recorded the temperature of
the apparatus at room temperature. After allowing the mouse to settle down for 10 minutes, I
attached the rubber stopper apparatus to the flask ensuring a good seal was made. I then placed
the pipette in a small beaker of water. As soon as the water hit the first graduation mark on the
pipette I began timing for 3 minutes. Once the 3 minutes was complete I recorded the final water
mark on the pipette and removed the rubber stopper. From that information I calculated the total
amount of oxygen consumed. This test was repeated three times. I then converted the volume of
oxygen consumed to metabolic rate (mL O₂/hr/g) and calculated the mean and standard deviation
of the three trials.
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After the testing at room temperature, I placed the flask inside an ice water bath and
allowed the temperature inside the flask to decrease to 5⁰ C. I then performed the same test as
before, repeated three times, including converting volume of oxygen consumed to metabolic rate
as well as the mean and standard deviation.
For the frog, I did a similar test. I got a frog that was in a small cage, ensuring there was
a small amount of water to keep it moist. I measured the temperature inside the cage to determine
room temperature. Instead of measuring the amount of oxygen consumed by the frog I measured
the breathing rate (number of buccal pumps) for a period of 60 seconds, repeating the test three
times.
I then placed the cage in an ice water bath. Once the temperature was lowered to 5⁰C, I
repeated the breathing rate test again three times, recording the number of buccal pumps in each
of the three 60 second periods. I then calculated the mean and standard deviation for the number
of buccal pumps for each temperature tested.
Results
The mean metabolic rate of the mouse at room temperature was 0.56 ± 0.11 mL O₂/hr/g
(Fig. 2). The mean metabolic rate of the mouse at 5⁰ C was 1.83 ± 0.25 mL O₂/hr/g. It is clear
that the metabolic rate of the mouse increased as temperature decreased. The mean number of
buccal pumps of the frog at room temperature was 126 ± 2.65 buccal pumps/min (Fig. 3). The
mean number of buccal pumps of the frog at 5⁰ C was 47 ± 1.73 buccal pumps/min. It is clear
that the metabolic rate of the frog decreased as temperature decreased.
Discussion
The results of my experiment matched my hypothesis that as temperature decreased the
metabolic rate of the mouse would increase and the metabolic rate of the frog would decrease.
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Endotherms maintain a constant body temperature and as temperature decreases, the cost to
maintain their body temperature increases so they must increase their metabolic rate. The results
of my experiment are congruent with what others have found, in that as ambient temperature
decreases, the metabolic rate of endotherms increases (Clark et al., 2010).
The metabolic rates of ectotherms are directly related to the ambient temperature.
Therefore, as temperature increases or decreases, the metabolic rates of ectotherms will also
increase or decrease. Killen et al. also concluded that as temperature increases, ectotherms must
consume more food to keep up with their increased metabolic rate (2010). Endotherms on the
other hand, must consume more food as temperature lowers to maintain their body temperature.
Literature Cited
Clarke, A., P. Rothery, and N.J.B Isaac (2010) Scaling of basal metabolic rate with body mass
and temperature in mammals. Journal of Animal Ecology 79:610-619.
Killen, S. S., D. Atkinson, and D. S. Glazier (2010) The intraspecific scaling of metabolic rate
with body mass in fishes depends on lifestyle and temperature. Ecology Letters 13: 184193.
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Figure 1. Makeshift volumeter. Soda lime was used in the bottom of the flask to absorb CO₂
exhaled from the mouse. Cotton was placed on top of the soda lime so the mouse did not come in
direct contact with the soda lime.
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Figure 2. Differences in metabolic rate of domestic mouse (Mus musculus) at room temperature
(26⁰ C) and 5⁰ C. Error bars represent the standard deviation of the metabolic rate at each
temperature.
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Figure 3. Differences in metabolic rate (respiratory rate) in Southern leopard frog (Lithobates
sphenocephalus) at room temperature (25⁰ C) and at 5⁰ C. Error bars represent the standard
deviation of the metabolic rate at each temperature.
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