First published online August 23, 2004
Journal of Experimental Biology 207, 3317-3327 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01143
Evidence that thyroid hormone induces olfactory cellular proliferation in salmon during a sensitive period for imprinting
Sean C. Lema* and
Gabrielle A. Nevitt*
Center for Animal Behavior and Section of Neurobiology, Physiology
and Behavior, One Shields Avenue, University of California at Davis, Davis, CA
95616, USA
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Fig. 1. Section of the olfactory epithelium showing BrdU-ir in single and clustered
cells. Positive staining appears as a black precipitate. (A) Typical round
morphology of a BrdU-ir cell in the basal cell layer. (B) Elongated morphology
typical of a BrdU-ir cell in the mid-apical cell layer. (C) An example of a
BrdU-labeled cluster of four cells situated in the basal region of the
epithelium. Labeled cells are black and appear to be in close juxtaposition to
each other. Length bars (10 µm) distinguish the extent of the basal region
in A, B and C. Scale bar in B, 10 µm.
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Fig. 2. Representative BrdU labeling in the olfactory epithelium of placebo fish
(A-C) and T3-implanted fish (D-F). Photomicrographs are shown from
six different individual fish. Scale bar, 40 µm.
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Fig. 3. Counts of BrdU-ir cells in the basal (A) and mid-apical (B) cell layers of
the olfactory epithelium of T3-implanted (black bars) and placebo
(gray bars) fish. Clustered and individual cells are considered separately in
the first two columns, and together in the third column (`total cells').
Values are expressed as means ± S.E.M.
Mann-Whitney U-tests: *P<0.05;
**P<0.025.
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Fig. 5. The distribution of cluster sizes from T3-implanted (black bars)
and placebo (gray bars) groups. Distributions are not significantly different
from each other ( 2=0.8289, P=0.9345).
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Fig. 6. (A) Profiles of body mass (triangles) and standard length (circles) plotted
against sampling date. Data are given as means ±
S.E.M. Numbers of fish sampled are shown in
parentheses. (B) Condition factor (see Materials and methods) plotted against
sampling date. Data are plotted as means ±
S.E.M. Sample sizes are identical to those
shown in A. Condition factor significantly decreased during the sampling
period, which is a trend associated with smolting (asterisks indicate
significant difference at overall P<0.05 between dates, Tukey HSD
test).
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Fig. 7. Profiles of plasma T4 (A) and T3 (B) across the
parr-smolt transformation. Data are plotted as means ±
S.E.M. Sample sizes for each date are shown
in parentheses in A.
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Fig. 8. Mean number of BrdU-ir cells (per 100 µm lamella length) plotted against
sampling date. Data are given as means ±
S.E.M. Basal cell counts are indicated by red
triangles; mid-apical cell counts are indicated by blue triangles. Data are
superimposed on a plot of mean plasma T4 levels for each sampling
date (black squares). Sample sizes for BrdU-ir cell data for each date are
shown in parentheses.
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Fig. 9. Mean number of BrdU-ir cells (per 100 µm lamella length) plotted against
mean plasma T4 levels for each sampling date. (A,B) Single and
clustered BrdU-ir cells considered together. The data indicate a significant
positive correlation in the basal cell layer (A) but not in the mid-apical
cell layer (B), suggesting that T4-induced proliferation is
restricted to the basal cell layer. (C,D) Single BrdU-ir cells only. The data
show a significant positive correlation in the basal cell layer (C) but not in
the mid-apical cell layer (D).
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© The Company of Biologists Ltd 2004
