Gonadosomatic index and circulating steroid hormone levels in male and female Astatotilapia burtoni. (A) Gonadosomatic index (GSI) differed among brooding, recovering, and gravid females, and between dominant territorial males and subordinate non-territorial males. (B) Circulating cortisol levels did not differ among females, or between male phenotypes. (C) Serum estradiol (E2) levels differed among females in all three reproductive states, and dominant males had higher E2 levels compared to subordinate males. (D) Circulating testosterone levels also differed among brooding, recovering, and gravid females, and were approximately 10-fold higher in dominant compared to subordinate males. (E) Serum 11-ketotestosterone levels differed among all three female groups, and dominant males had 10-fold higher levels than subordinate males. Data are plotted as mean ± SE. Bars with different letters within a sex represent significant differences (p < 0.05) and sample sizes are indicated within each bar.