Fig. 1

Sperm motility and birth rate. Time-course changes during thermal stress response assay of the sperm motility parameters average motility (a), progressive motility (b), curvilinear velocity (VCL) (c), Beat Cross Frequency (BCF) (d) and Linearity (LIN) (e) after continuing incubation at 37 °C. For this analysis, cauda epididymis spermatozoa of FL2 and Ctrl mouse line (n = 10 per group) were extracted and incubated at 37 °C for 5 h. Each point represents the mean of 8 defined chamber partitions viewed and measured using the Computer-assisted sperm analysis (CASA) system. The experiment has been statistically evaluated for the two factors time and mouse line effect using two-way ANOVA (GraphPad Prism) as indicated in the graph. Birth rate (f) of ‘high-fertility’ mouse line FL2 (orange) and Ctrl line (green) is visualized providing information about portion of successful line-specific matings. Each of the 14 points represents the average birth rate per generation. These data were acquired over a 4-year period with generation population sizes ensuring at least 60 matings. The groups were tested for normal distribution and analyzed by two-tailed t-test (***, p < 0.001)