Figure 1.
Proposed steroidogenic pathways.
Because steroidogenic pathways in sticklebacks have not been elucidated, steroidogenic pathways in rainbow trout are shown here [46], [49], [50], [81]. Steroidogenic enzymes are shown in red. HSD, hydroxysteroid dehydrogenase; P450, cytochrome P450.
Figure 2.
Divergence in sex steroid levels.
Comparison of plasma 11-ketotestosterone (A), 17β estradiol (B), and testosterone (C) between Pacific Ocean and Japan Sea forms of threespine stickleback. The sample size is shown above each column. Lower case letters above the bars indicate samples that are significantly different from each other (Tukey HSD test after ANOVA).
Figure 3.
Correlations between plasma testosterone and other sex steroid hormone levels.
Correlations between log-transformed plasma testosterone levels and log-transformed plasma 17β estradiol levels in females (A) and correlations between log-transformed plasma testosterone levels and log-transformed plasma 11-ketotestosterone levels in males (B). Solid lines and dotted lines indicate regression lines for the Japan Sea form and the Pacific Ocean form, respectively. Closed circles, Japan Sea form; open circles, Pacific Ocean form.
Figure 4.
Relative expression levels of mRNA in the pituitary glands for LHβ and FSHβ, determined by qPCR.
The sample size is shown above each column.
Figure 5.
Correlation between log-transformed testosterone levels and log-transformed standard length in males.
Solid lines and dotted lines indicate regression lines for Japan Sea form and Pacific Ocean form, respectively. Closed circles, Japan Sea form; open circles, Pacific Ocean form. The slopes of the two regression lines were not significantly different (see the text).
Figure 6.
Divergence in the expression levels of steroidogenic enzymes between the gonads of Pacific Ocean and Japan Sea forms.
(A) Microarray analysis of testis. Heat map and clustering analysis of the transcripts of genes encoding steroidogenic pathways are shown. Different lines represent different probes. For most genes, multiple independent probes were designed for the same gene. Cluster analysis of probes (shown on the left side of the heat map) indicates that signals of different probes representing the same gene product gave rise to similar signals. Different columns indicate different fish (n = 4 males for each form). In the heat map, red colors indicate high fluorescence signals, while green colors indicate low fluorescence signals. Asterisks indicate that the fluorescence signals that were significantly higher in the Japan Sea males than in the Pacific Ocean males by ANOVA; *, P<0.05; **, False Discovery Rate-corrected P<0.05. (B) qPCR analysis of the transcripts of genes encoding two enzymes involved in the conversion of testosterone into 11-ketotestosterone, 11β-hydroxylase (CYP11B1) and 11β-hydroxysteroid dehydrogenase (HSD11B2) (n = 4 fish for each form).