Figure 1. Seasonal differences in hair bundle density in the female midshipman saccule. A, Phalloidin-labeled hair bundles were counted in 10,000 μm2 areas from seven regions across the saccule, as indicated by the numbered boxes on the line drawing (left). The micrographs (right) show representative images from the middle of the saccule from a nonreproductive female and a reproductive female. Scale bar, 20 μm. R, Rostral; D, dorsal. B, Hair bundle quantification from these seven saccular regions. Data were pooled over three summer (reproductive) and two winter (nonreproductive) sampling seasons. There was a significant effect of reproductive state (F(1,326) = 70.77, p < 0.0001) and saccular region (F(6,326) = 48.27, p < 0.0001) but not of the interaction between the two (F(6,326) = 1.302, p = 0.25), as determined by two-way ANOVA. Significantly more hair cells were seen in regions 2, 4, 5, 6, and 7 of reproductive females compared with nonreproductive females (a prior t tests for paired comparisons were used to determine differences in bundle density between the same regions in nonreproductive and reproductive fish; **p < 0.01, ***p < 0.001). Error bars are mean + 1 SEM. n = 18–19 saccules from nonreproductive females, n = 28–29 saccules from reproductive females. The variation in sample size occurred because some saccular regions suffered dissection damage and were therefore not used for bundle quantification. Black bars, Nonreproductive females; gray bars, reproductive females.