Three-dimensional principal component analysis of differentially expressed genes. The 7,447 differentially expressed features (FDR 5%; relative fold change >1.5) were used to assess the global view of each animal’s contribution to the life cycle expression profile. Each sphere represents the composite expression profile of one animal according to the top three principal components plotted in three-dimensional space (ArrayTrack). The spheres are colored by similar age group (N = 4 or 5). The spheres with black vertices indicate females, while those without indicate males. Animals generally cluster together according to respective age and sex in an age-sequential pattern. Figure 1A, B shows different views of the same plot: (A) highlights the age-related pattern, while (B) best displays the sex divergence in expression. The top three principal components accounted for 32.5%, 13.8%, and 10.8% of the total variance.