Percentage (%) of chymotrypsin-like (CT-L), trypsin-like (T-L) and peptidylglutamyl peptide hydrolysing or caspase-like (PGPH) proteasome activities in brain extracts of killifish of different ages. n >=6 per sample group; error bars indicate standard error of the mean. ** p < 0.005, *** p=0.0001, **** p < 0.001, one-way ANOVA, Holm-Sidak's multiple comparison test. For each sample group, the mean value of each activity in young samples (5 wph) was set to 100%. 