Antecdotal but....I posted awhile back on one of the Tanganyikan threads that I had a large aquarium with 4 adult, wild caught, Lepidiolamprologus nkambae, with one male and three females. Very easy to sex, as the genital opening in all three females was approximately 3 mm wide, while in the male only 1 mm wide. The male was also 1 cm longer in length with greater body mass. Soon after recieving them, the male paired off with one female and spawned, producing approximately 100 fry. 5 more spawns took place around every 30 to 35 days. Six months later the male went blind and died. About one month after that, two of the females paired off and spawned, producing approx. 50 fry.
The only explanations I can come up with is that the female, which paired off with the originally spawning female, changed its sex to that of a male, or it was a male all along, mimicking a female so convincingly, that even its genital opening appeard like that of a females genital opening.