First published online March 17, 2006
Journal of Experimental Biology 209, 1261-1273 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02058
Chemoreceptor plasticity and respiratory acclimation in the zebrafish Danio rerio
B. Vulesevic,
B. McNeill and
S. F. Perry*
Department of Biology, University of Ottawa, 10 Marie Curie, Ottawa,
ON K1N 6N5, Canada
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Fig. 1. Representative raw data acquisition recordings illustrating the voltage
changes measured in the water of (A) a fish undergoing spontaneous breathing
and (B) the same fish after in situ anaesthesia with benzocaine.
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Fig. 2. The relationships between breathing parameters as measured by analysis of
video recordings or from computerized data acquisition. (A) Correlation
between breathing frequencies (fR) determined by the two
methods based on analysis of six different fish exhibiting a wide range of
fR (r2=0.999,
y=0.986x+0.687). (B) Correlation between opercular
displacement (a measure of breathing amplitude) determined by the two methods
during normocapnia and hypercapnia (PwCO2=3.5 mmHg). Each
plot represents a change in amplitude of a single fish and each fish is
represented by a different symbol (N=6). (C) Changes in ventilation
amplitude during filming were analogous regardless of the method of
measurement; data plotted are taken from B (r2=0.968,
y=0.819x+0.119); N=6.
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Fig. 3. (A) Frequency of breathing pauses and (B) proportion of total breathing
occupied by apnea in s min–1 in zebrafish during normoxia
(black bars; N=4 pausers out of 10 fish) and during hyperoxia (white
bars; N=8 pausers out of 10 fish). (C,D) Representative original data
recordings from normoxic (C) and hyperoxic fish (D).
 Statistically significant difference (P<0.05)
between the two groups.
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Fig. 4. The frequency of breathing pauses (A,C) and the proportion of total
breathing occupied by apnea (B,D) in control (black bars, N=7) and
hyperoxia pre-exposed (white bars, N=8) zebrafish Danio
rerio exposed to acute hypoxia (A,B) or acute hypercapnia (C,D).
Statistically significant differences (P<0.05) *within the groups;
between the two groups.
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Fig. 5. Respiratory responses of zebrafish Danio rerio to acute hypoxia
(A,B) or hypercapnia (C,D). Control fish were taken directly from the main
zebrafish facility (filled circles, N=12) and were monitored in
normal water for a similar period of time as the experimental fish (kept for
28 days in normoxic/normocapnic water) and acutely exposed to hypoxia or
hypercapnia (unfilled circles, N=9 for hypoxia; N=14 for
hypercapnia). (A,C) Changes in breathing frequency (fR);
(B,D) changes in relative breathing amplitude (opercular displacement).
*Significant differences within the control or experimental groups;
significant differences between the control and
experimental groups; two-way RM ANOVA (P<0.05).
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Fig. 6. The effects on ventilation amplitude (relative opercular displacement) in
zebrafish Danio rerio of changing water pH with, or without,
accompanying hypercapnia. One group of fish (right) was exposed to an increase
in PwCO2 from 0.3 to 3.5 mmHg, causing pH to change from
7.4 to 6.3 (filled bars; N=14). Another group of fish (left; unfilled
bars; N=8) was subjected to a change in water pH only from 7.4 to 6.3
at constant PwCO2 of 0.3 mmHg. *A significant change in
opercular displacement; one-way RM ANOVA (P<0.05).
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Fig. 7. (A,C,D) The respiratory responses of zebrafish Danio rerio
pre-exposed to hyperoxia (PwO2>350 mmHg) for 28 days
(unfilled circles) to (A) acute hypoxia (N=12), (C) hypercapnia
(N=8) or (D) sodium cyanide (N=7) compared to the responses
of control fish (filled circles; N=12 different fish for each
treatment). (B) Average rates of change of breathing frequency
(fR) between 40 (Control) and 155 mmHg (Hyperoxia) for the
two groups. *Significant differences within the control or experimental
groups; significant differences between the control and
experimental groups; two-way RM ANOVA (P<0.05).
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Fig. 8. Serotonin-immunoreactive (5-HT-IR) neuroepithelial cells (NECs) of the gill
filament (F) in zebrafish Danio rerio. (A) 5-HT-IR NECs along
the filament in a control fish; (B) 5-HT-IR NECs along the filament at higher
magnification in a hyperoxia pre-exposed fish; (C) higher magnification of
double labeled 5-HT-IR with associated nerve fibers (ZN-12-IR) of the proximal
filament epithelium in a control fish. Scale bars, 100 µm (A); 10 µm
(B,C).
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Fig. 9. The respiratory responses of zebrafish Danio rerio pre-exposed to
hypoxia (PwO2=30 mmHg PO2) for 28 days
(unfilled circles) to (A) acute hypoxia (N=8), (B) hypercapnia
(N=7) or (C) sodium cyanide (N=6) compared to the responses
of control fish (filled circles, N=12 different fish for each
treatment). *Significant differences within the control or experimental
groups; significant differences between the control and
experimental groups; two-way RM ANOVA (P<0.05).
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Fig. 10. The respiratory responses of zebrafish Danio rerio pre-exposed to
hypercapnia (PwCO2=9 mmHg) for 28 days (unfilled circles)
to (A) acute hypoxia (N=11), (B) hypercapnia (N=11) or (C)
sodium cyanide (N=8) compared to the responses of control fish
(filled circles, N=12 different fish for each treatment).
*Significant differences within the control or experimental groups;
significant differences between the control and
experimental groups; two-way RM ANOVA (P<0.05).
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© The Company of Biologists Ltd 2006
