The Conditioning of Respiration Rate in Goldfish (Carassius auratus)
Using Water Temperature and Visual Stimuli
Donna Tehrani and Patrick Schafer
Department of Biological Sciences
Saddleback College
Mission Viejo, California 92692
Goldfish (Carassius auratus) is a domesticated species of tropical fish that is often
used in psychological and physiological experiments. They have been demonstrated
to respond to classical (Pavlonian) conditioning and even alter their homeostatic
processes based on various stimuli, including color. Twenty goldfish were trained to
associate the color red with a decrease in water temperature and the color green
with no change in water temperature. An experiment was run to see whether
goldfish exposed to the color red would change their respiration rates even without
a change in temperature by filming and recording their operculum movements. The
change in operculum movements for one minute before and after exposure to the
stimuli was compared to a control group which was shown the color green instead.
A two-tailed t-test was performed to ascertain the difference between the changes in
respiration rates between the two groups. There was no significant difference
(p=0.084), which suggests that some fish do not alter their respiration rates in
anticipation of temperature changes.
Project Summary
Most species of tropical fish, including carp and goldfish, have superior color
vision to humans or other mammals due to the structure of their retina. Therefore, it is
unclear to what extent fish use visual cues to anticipate environmental changes, since
they can respond to stimuli that are too subtle for humans to notice. They also possess the
ability to be psychologically and physiologically conditioned as a response to visual
stimuli. Previous research suggests that it may be possible that goldfish can anticipate
changes in their environment and modify their homeostatic processes. Goldfish possess
color vision, and have demonstrated color constancy in a laboratory setting (Ingle 1985).
It has also been shown that because of the structure of the brain and eye, goldfish are
more adept at recognizing colors than patterns, especially different shades of green and
red (Ingle 1965). In laboratory studies, goldfish have been shown to lower their
respiration rates in response to lower temperatures (Schmidt-Nelson 1997). Also,
Japanese carp, a closely related species, have demonstrated the possibility of respiratory
conditioning using electrodes (Woodard 1971, Otis 1957). However, no research was
found regarding the possibility of conditioning goldfish using temperature and color as a
visual stimuli. We hypothesized that when goldfish were trained to associate a specific
color with changes in water temperature, they would alter their respiration rates when
shown the stimuli but without a change in temperature. This research could shed light on
the extent that aquatic creatures regulate their homeostatic processes based solely on
sensory information.
Methods and Materials
Twenty feeder goldfish were purchased from Petsmart and were trained over a
period of two weeks. Training consisted of placing an individual goldfish with 0.5 L of
water at 18-23 ̊C into a cylindrical plastic container that was 18 centimeters across 46
centimeters high. The goldfish was given five minutes to acclimate itself to its
surroundings, after which the container was completely surrounded by a red letter-size
folder and 0.5 L of water at 0̊ C were poured in to decrease the respiration rate. The
goldfish was kept in this condition for another five minutes, before being returned to one
of two common tanks. After a couple hours, the same goldfish was placed in the same
container with the same amount of water. After five minutes the container was
surrounded with a green letter-sized folder instead and 0.5 L of room temperature water
was poured inside the container. Each fish was exposed to both temperatures and colors
daily, and the order in which they were placed in each condition was varied. After 14
days of conditioning, an experiment was run where 10 of the goldfish were randomly
placed into the glass container and filmed by a Canon SX 150IX camera. Randomization
was achieved by removing the goldfish from their two common tanks one at a time and
alternating between placing them in the control and experimental group. After a four
minute acclimation period, the number of operculum movements in one minute was
recorded. The red folder was then displayed but 0.5 L of room temperature water were
poured instead, and the number of operculum movements in the minute after the water
was added was recorded. The procedure was repeated with the other 10 fish, except the
green folder was displayed instead. The change in respiration rates between the two
groups was recorded and an unpaired two-tailed t-test was performed between the groups.
Results
The mean change in respiration rates in the experimental group was 2.9 ± 3.2 (±SEM,
n=10), and mean change in respiration rates in the control group was -1.4 ± 6.7 (±SEM,
n=10). The two groups were graphed against their mean change and we obtained a pvalue of 0.084, using a two tailed t-test, which corresponds to no significant difference in
the number of operculum movements between the two groups (Figure 1). Therefore, our
data suggest the null hypothesis.
Figure 1. This bar graph displays the average change in respiration rates between the
experimental (n=10) and control group (n=10). A two-tailed unpaired t-test was
performed on the difference in operculum movements, and there was no significant
difference between the two groups (p=0.084). Standard error bars are shown.
Discussion
Our results suggest that goldfish do not make immediate changes to their
respiration rates even when they anticipate changes in water temperature. However, we
cannot rule out the possibility that competing trends may have affected out results, since
goldfish, like terrestrial animals have been shown to increase heart rate and respiration
rate in anticipation of stress (Woodward 1971).
Further experimentation might be performed by raising the temperature of the
water instead of cooling it down, to see if this was the case. Also, more extreme changes
in temperature might be employed to maximize the physiological stress and make a
possible response more visible. Finally we could measure heart rate instead of respiration
rate.
In conclusion, it does not appear that goldfish physiologically prepare themselves
for changes in water temperature before the changes occur. With extreme changes in
water temperature caused by industrial activities such as runoff from nuclear power
plants, it is essential to see the degree to which aquatic creatures are able to adapt.
Literature Cited
Ingle, D. The Goldfish as a Retinex Animal. 1985. Science 4687(227): 651-654
Otis, S. Conditioned Inhibition of Respiration and Heart Rate in the Goldfish. 1957.
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Schmidt-Nielsen K. Animal Physiology: Adaptation and Environment. 1997. Cambridge
University Press.
Ingle, D. Interocular Transfer in Goldfish: Color Easier than Pattern. 1965. Science
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Woodard, W. Classical Respiratory Conditioning in the Fish: CS Intensity. 1971. The
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