Figure 1.

The relationship between the proportion of NAD(P)H bound to protein and the fluorescence lifetime of 1-pyrene butyric acid (PBA) in sperm of the cricket Gryllus bimaculatus. The proportion of NAD(P)H bound to protein is a measure of sperm metabolic rate whereas PBA fluorescence lifetime is inversely related to the production of ROS (see §2). (a) Individual samples obtained from freshly ejaculated sperm (solid circles) and stored sperm (open circles). (b) The same data shown for male means (solid circles) or female means (open circles). Sperm of some males were obtained after ejaculation as well as from storage (paired design; see figure 2 and electronic supplementary material, figure S1 and table S2 for paired comparisons). The reversal of the relationship between metabolic rate and oxygen radicals production effect in the female is significant (t = 5.617, P < 0.001; electronic supplementary material, table S2). Linear regressions carried out separately for ejaculated and stored sperm show the non-significant individual trends for stored sperm (broken line) and ejaculated sperm (solid line; electronic supplementary material, tables S3 and S4).