Cadmium disrupts behavioural and physiological responses to alarm substance in juvenile rainbow trout (Oncorhynchus mykiss)
Graham R. Scott1,*,
Katherine A. Sloman1,
Claude Rouleau2 and
Chris M. Wood1
1 Department of Biology, McMaster University, 1280 Main Street West,
Hamilton, Ontario L8S 4K1, Canada
2 National Water Research Institute, PO Box 5050, 867 Lakeshore Road,
Burlington, Ontario L7R 4A6, Canada
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Fig. 1. Diagrammatic representation of the observation tank. Fine sewing thread was
placed on the outside of each tank to indicate the tank midline (dotted line).
A fish scored one midline crossing each time its head (from snout to end of
operculum) passed the midline. Tanks also contained a shelter and air stone
and a point of introduction for food and alarm substance. Diagram not to
scale.
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Fig. 2. Mean change in (A) the number of midline crossings, (B) the number of
feeding bites, (C) the latency to first feed and (D) the time spent under
shelter before and after stimulus for different cadmium (Cd) exposures
(N=16 for each group). * represents a significant difference from the
DDW (distilled deionized water) control (P<0.05).
 represents a significant difference from the skin extract
control (P<0.05); ** represents a significant difference from the
DDW control (P=0.001) using an unpaired t-test only.
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Fig. 3. (A) Schematic representation of the fish olfactory system, portraying cell
bodies and dendrites of olfactory neurons within the olfactory epithelium.
Axons of olfactory neurons extend via the olfactory nerve to the
olfactory bulb where they synapse with post-synaptic bulbar neurons (after
Hara, 1986 ). The broken line
indicates the theoretical boundary separating the olfactory bulb from the
olfactory nerve. (B) Sagittal whole-body autoradiogram showing
109Cd accumulation after 7-day Cd exposure followed by 2-day
depuration in control water. (C) Corresponding whole-body tissue section. OR,
olfactory rosette; ON, olfactory nerve; OB, olfactory bulb.
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Fig. 4. (A) Accumulation of cadmium (Cd) after 0, 3, 5 and 7 days exposure, as well
as 7 days exposure followed by a 2-day depuration period in control water, in
the olfactory rosette, olfactory nerve and olfactory bulb. Calculated Cd
accumulation (right-hand y-axis) was determined as described in
Materials and methods. All points within each tissue are statistically
distinct (P<0.05) before transfer to control water (depuration
period). (B) Concentration index relative to mean fish liver concentrations
for the olfactory rosette, olfactory nerve and olfactory bulb. * represents a
significant difference between fish exposed for 7 days and those exposed for 7
days followed by 2 days of depuration (P<0.05).
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Fig. 5. Liver, kidney, gill and whole-body cadmium burdens for 0 µg Cd
l–1 (control), 2 µg Cd l–1 (7-day
waterborne exposure) and 3 µg Cd g–1 (7-day dietary
exposure at 1% daily ration). Each exposure was followed by a 2-day depuration
period in control water (N 17 for each group). * represents a
significant difference from the control (P<0.05).
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Fig. 6. (A) Plasma cortisol and (B) plasma ion concentrations before (control) and
at increasing time points after introduction of skin extract into tanks
(N=10 for each group). * represents a significant difference from the
control (P<0.05).
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© The Company of Biologists Ltd 2003
