Fig. 2. Experimental timeline used for Haplochromis burtoni females. Different reproductive and nutritional states were examined for levels of gonadotropin-releasing hormone (GnRH) expression in females (study IV). Females were observed until the act of spawning. A subset of these (Spawners; Sp) was removed for blood sampling and then killed for determination of body and gonad masses and GnRH mRNA levels. The remainder were divided into three groups. Brooders (Br) were females that brooded fry in their mouths for 2 weeks after spawning. Broodless females (Br-) were females whose eggs were removed immediately following spawning. Of these, half were fed (Br-F+) and the other half were food-deprived (Br-F-). At the end of 2 weeks, brooders were removed for blood sampling, and all three groups were killed for determination of relative gonadal masses and of GnRH mRNA levels. GSI, gonosomatic index (see Materials and methods).