Espinosa 1

The Effect of Variable Light Intensities on the intake of O2, and Myocardial Contractility Rate of Gerbillinae Muridae (Common Gerbil)

Cisco G. Espinosa

Hudson County Science Fair

March 2, 2015

This research was supported in part by a grant from the CarePoint Health Foundation.

Table of Contents

Abstract………………………………………………. 3

Review of Literature………………………………….4

Hypothesis…………………………………………….6

Procedure…………………………………………..…6

Results………………………………………………....7

Conclusion…………………………………………...…22

Bibliography………………………………………....…16

Abstract

The purpose of this study was to test the effect of variable light intensities on the vital signs of gerbils, and how this effect varied by gender. It is thought that most organisms react differently to a variety of stimuli including light intensity. It is also known that light, specifically, can cause a certain level of stress or anxiety, which would alter the vital signs of an animal. For example, flashing lights may cause a patient with epilepsy to go into seizure considering that they have photosensitive epilepsy. Different intensities of light also startle, and disturb animals in their habitats, especially if those animals are nocturnal, which is the reason for which many zoos, and areas of animal studies ask for no flash photography. This study measured the vital sign of oxygen intake of gerbils, and using this data, myocardial contractility rates were formulated. This study was performed by placing one gerbil, male or female, in a measurement chamber and allowing for one intensity of light to be shone on them.

The intensities of light were categorized as low, middle, or high intensities based on the position of the dimmer switch, the values measured on the photometer, and the judgment of the scientist in charge. Following testing the gerbils were returned to their habitat temporarily, in order to calm them for the following test. In this study, there were mixed, and controversial results, which both supported and refuted the original hypotheses which stated that, when a higher intensity of light is shone on an organism, in this case gerbils, the vital signs of this organism would increase. This then in turn led to the second conclusion that the fluctuation in female vs. males varies by the individual of that species. Different stimuli have different effects on the variation of vital signs in organisms. Furthermore, one must note that external factors can contribute to any and all data collected, and that the reduction of external factors raise the external validity of a study.

Literature Review

The topic of use of flash photography near or around animals is highly debatable. Some claim that it is necessary to use flash photography in order to get a better visual aspect of an animal in its habitat, or in any habitat, or in general. However one must be considerate of the risks involved with using flash photography around certain species of animals. Clearly, the use of flash photography on photosensitive animals is very dangerous, just as the flashing of lights can be very dangerous to humans. Photosensitive seizures and epileptic attacks can occur in certain people (1 of 4,000) when exposed to flashing lights (Bladon Medical Publishing, 2005). With this in mind, the possibility that flashing lights may be a health risk to other organisms must be considered. Firstly, the retina of animals consist of rod cells for nocturnal motion sensory, and cone cells for diurnal activity (Olivero and Cohen, 2004). Gerbils being primarily nocturnal animals, can be considered photosensitive since they have a higher rod to cone cell ratio (Roberto Refinetti, 1999; Olivero and Cohen, 2004). A study performed on seahorses by Dave Harasti, produced results which showed that flash photography truly didn’t have effects on the longevity of seahorses, however it is known that seahorses are creatures that tend to live in shallow waters where light enters, so their sensibility to light variation would be less than that of other creatures (Harasti and Gladstone, 2011).

In humans, flash photography has several effects that may become permanent after allotted periods of time. Some of the immediate effects include the red-eye effect in which organisms with tapetum lucidum reflect the color red, or any color, especially small animals, different from the organism’s regular eye color. However more long term effects include, permanent damage to the retinal nerve cells of an organism’s eyes, which can lead to loss of vision, or blurriness of vision in the future (Olivero and Cohen, 2004 ). Apart from causing epileptic seizures, and long term damage to the eyes, sudden bursts of light also cause stress on many animals as well as humans. This stress in turn has different effects on the variability of heart rates and respiration rates of humans (Bernardi et al., Wdowczyk-Szulc et al., Valenti et al., Castoldi et al., Passino et al., Spadacini et al., and Sleight, 2000). Depending on an organism and its anatomy, this rate of variability changes. For example, the lung capacity of a gerbil can be estimated to be approximately 1.2 ml (Canals, Olivares, and Rosenmann, 2005). This would allow for the conclusion to be made, that the respiratory rate of a gerbil would be drastically different than that of a human for example, which has a lung capacity of 6.0 L.

While many of the previously mentioned studies had undeniably well written data, there were some gaps in the research of all of them. These studies don’t suggest measuring the stress levels of different animals besides humans. While humans may be the main priority of the world, there are many studies which depend on the calmness, and relaxation of certain animals, and many professions where the conditions in which an animal lives are critical information. For example, veterinarians many times have to perform autopsies on larger animals by request of the family, or owners, or for research. In a case where the animal died due to sudden stimuli that caused it to have a myocardial infarction, certain tell-tale signs would be necessary to conclude this. Having this information would be helpful to these professionals in need of further knowledge. This study can also be considered a micro study used for reference in other studies such as the migration patterns of different species around the world. As is known by most people, global warming is a factor which is going to begin to have impacts on species of animals as well as humans. The effect of different intensities of light can be representative of changing in daylight hours, and temperatures on the Earth. This in turn would alter with the migration patterns of certain animals, and if a species were to not adapt to these new changes, it could mean that evolution would naturally eliminate certain species of animals, messing with food webs, and chains.

While it can be understood that humans have more importance in the field of science, animal sciences have just as much importance, and if scientists plan on testing on smaller mammals, or non-human test subjects they should maintain a level of external validity. In any test there are a set of sub factors which have relevance to the outcome of a research study (Lynch, 1982). External validity determines the credibility of results based on included external factors, and coincidental relationships between them and the results of a study (Calder, Phillips, and Tybout, 1982). In the case of these studies, external factors that could be measured in a future study would be an immediate change in light intensities, and sounds when taking these measurements.

Hypothesis

If gerbils are exposed to higher intensities of light, then the intake of O2, and myocardial contractility rate of the gerbils will increase greatly in the first few moments in which measurements are taken, and then gradually decrease as the experiment progresses. Furthermore the fluctuation in the intake of O2, and myocardial contractility rate in the female gerbils will be lower than that of the males.

Procedure

This study followed a strict procedure in order to attain the most accurate readings. The study began with the preparation of the Vernier Labquest 2 Data Collector with Photometer (range: 0-600,000), and O2 Probe. Then the light cart with dimmer, in order to achieve variable light intensities, was prepared in a corner of a room where little noise echoed to, and an outlet was nearby. Following this, marks were made on the dimmer switch using tape, this directed to what place on the dimmer was considered of low, medium, or high intensity, this was then calibrated using the photometer. Then one of the two gerbils, male or female, was placed in the 1,900 ml measurement chamber. Following this the light had to be dimmed to the proper setting, and then data collection would begin. Lastly the data collection stopped, and the gerbil was placed back into its habitat for at least five minutes, and during that time the other gender was tested. Due to certain design flaws, this procedure was repeated almost identically the same, however in the secondary procedure the range for the photometer was 0-600 lux, and in the third procedure the range for the photometer was 0-6,000 lux. The first two ranges for the photometer led to erroneous data collections. For the most accurate results, this test was performed in a room where very few people were present, and little noise was made. For the control tests, the light intensity which normally shines on the organism's home was measured, not the light intensity of the room or of another room. This contributes to the external credibility, in knowing that the results gained were not due to a sudden stimulation of the subject, rather than the one stimulation that is being used on the subject.

Results

Key:

●113/430 = BPM/X, X= 430(BPM)/113- ratio which was compared to gerbil respiratory rate to calculate myocardial contractility rate, made by averaging the highest and lowest values in the healthy range for that measurement . This ratio was created using the work of Drs. Foster and Smith, using their calculated averages of heart rate and respiration rates of gerbils, this formula was made by taking the average respiration rate over the average heart rate for the gerbils. This was then compared to the respiration rate of the subjects.

●avg. - Average

●BPM= breaths per minute

●# ppm- part per million of said gas in air

●. #% addition/reduction- amount of change in regards to air

●# lux- light intensity average per square meter

Averages of Heartbeats and Breaths per Minute (Smith and Foster, 1999)

Average Heart Beats per Minute
260-600
(430) / Breaths per Minute
85-140
(113)
Control Testing Results / Light Intensity:Control / External Conditions and Notes During Test
Female: / Myocardial Contractility Rate:873 beats per minute
O2Intake Rate:avg. 837.5 ppm (.08375% oxygen reduction)
BPM:229
Lux Average:495.7 lux / During this test, three people were present in the room, and they made minimal noise. There were little amounts of whispering between the two people closest to the test subject, but it did not seem to be affected by them. The gerbil was biting at the bottom of the probe, and it attempted to scratch at the walls of the chamber in trying to escape.
Male: / Myocardial Contractility Rate:201 beats per minute
O2Intake Rate:avg. 350 ppm (.035% oxygen reduction)
BPM:53
Lux Average:919 lux / During the taking of measurements for this test there were three people present making minimal noise. There were footsteps, whispering, and tapping from the movement of the photometer. The gerbil in typical response scratched at the chamber since they are naturally tunneling creatures.

Female Results:

Results of Tests onG.muridae / Intensity 1 / Intensity 2 / Intensity 3
Test 1 / Myocardial Contractility Rate:29 beats per minute
O2Intake Rate:113.3 ppm (.01133% oxygen reduction)
BPM:9
Lux Average:
447.63 lux / Myocardial Contractility Rate:55 beats per minute
O2Intake Rate:143.8 ppm (.014375% oxygen reduction)
BPM:14
Lux Average:725.3 lux / Myocardial Contractility Rate:221 beats per minute
O2Intake Rate:646.7 ppm (.06466% oxygen reduction)
BPM:67
Lux Average:483.4 lux
Notes / During this test there were three people present in the room.There was some whispering, and tapping when trying to fixate the photometer. During this time, tables were being moved in the background, away from the testing area. The gerbil was biting at the bottom of the probe, and it attempted to scratch at the walls of the chamber in trying to escape. / During this test there were three people present in the room.There were tables moving in the background, and minimal talking between the two people farthest from the test subject. The subject scratched at the chamber, and bit the bottom of the probes in an attempt to escape. / During this test there were three people present in the room making some noise. Some tables were being moved in the background, however the test subject was somewhat secluded from that noise, and it didn’t seem to affect the test. As usual, the gerbil scratched at the chamber, and bit the bottom of the probes in an attempt to escape from the chamber.

Male Results:

Results of Tests onG. Muridae / Intensity 1 / Intensity 2 / Intensity 3
Test 1 / Myocardial Contractility Rate:136 beats per minute
O2Intake Rate:263.1 ppm (.02631% oxygen reduction)
BPM:41
Lux Average:
129.8 lux / Myocardial Contractility Rate:123 beats per minute
O2Intake Rate:346.6 ppm (.03466% oxygen reduction)
BPM:37
Lux Average:1,123.44 lux / Myocardial Contractility Rate:-1,097 beats per minute
O2Intake Rate:avg. -37,100 ppm (-3.71% oxygen reduction)
BPM:-331
Lux Average:78.73lux
Notes / During this test there were four people present, making little to no noise. There were some tapping noises when attempting to fixate the photometer into its place, but other than that there was no noise that could affect the reactions of the gerbils. The gerbil was biting at the bottom of the probe, and it attempted to scratch at the walls of the chamber in trying to escape. / During this test there were four people present, making little to no noise. There were some tapping noises when attempting to fixate the photometer into its place, but other than that there was no noise that could affect the reactions of the gerbils. The gerbil was biting at the bottom of the probe, and it attempted to scratch at the walls of the chamber in trying to escape. / During this test two people were present. There was minimal whispering, and a bit of tapping from the positioning of the photometer. The gerbil as usual scratched at the chamber walls, and bit at the probe bottoms in an attempt to escape from the chamber.

Oxygen -Test 1 Graph:

Light Intensity- Test 1 Graph:

Replication 1:

Control Testing Results / Light Intensity:Control / External Conditions and Notes During Test
Female: / Myocardial Contractility Rate:-410 beats per minute
O2Intake Rate:avg.-1,037.5 ppm (-.10375% oxygen reduction)
BPM:-124
Lux Average:744.45 lux / The habitats of both the male and female gerbils were in the same room as the test subject, and they were squeaking and running on their wheels. However it is most probable that they had very little to no impact on the results of the test subject, since they were separated, and the subject was in an enclosed environment where very little sound enters. Furthermore there were several people present in the room who made very little noise. The subject’s Only disturbances came from the positioning of the photometer in alignment with the chamber, and consistent with prior behavior, the gerbil scratched at the walls of the chamber, and bit at the bottom of the probes in an attempt to escape.
Male: / Myocardial Contractility Rate:41 beats per minute
O2Intake Rate:avg. 156.2 ppm (.01562% oxygen reduction)
BPM:12
Lux Average:769.98 lux / During this test there were three people present, and a printer was working in the background. The three people were not speaking, and the habitats of the subject and its female counterpart were present. The other gerbils made noise in their habitats, however this didn’t seem to affect the test subject. Customarily, the subject attempted to escape from the chamber by nibbling at the bottom of the probes, and scratching at the walls of the chamber.

Female Results:

Results of Tests onG. Muridae / Intensity 1 / Intensity 2 / Intensity 3
Replication 1 / Myocardial Contractility Rate:61 beats per minute
O2Intake Rate:avg. 156.2 ppm (.01562% reduction)
BPM:18
Lux Average:401.66 lux / Myocardial Contractility Rate:114 beats per minute
O2Intake Rate:avg. 268.7 ppm (.02687% oxygen reduction)
BPM:34
Lux Average:721.23 lux / Myocardial Contractility Rate:49 beats per minute
O2Intake Rate:avg. 140 ppm (.014% oxygen reduction)
BPM:15
Lux Average:723.38 lux
Notes / During the taking of measurements for this test there were two people present in the room. One left creating footsteps as they left, and the other remained collecting data. As usual the alignment of the photometer caused some noise that didn’t seem to startle the subject, and the gerbils in the background didn’t seem to have an effect on the subject either. Consistent with previous behavior the subject scratched at the walls of the chamber, and bit the bottom of the probes in an attempt to escape. / While this test was taking place there was a minimal amount of noise being created. The fixation of the photometer, and the sounds of gerbils squeaking in the background made up the majority of the noise in the room.
The gerbil per usual was scratching at the chamber walls, and biting at the bottom of the probes. / This test was taken during a time when there was only one person present, and no noise was made other than the fixation of the photometer. The subject was calmer during this test, it only bit at the probes for a short time, and scratched momentarily, but then proceeded to walk around the chamber.

Male Results: