Energy expenditure for mouthbrooding in a cichlid fish

Summary Energy costs of mouthbrooding were investigated in the East African maternal mouthbrooder Pseudocrenilabrus multicolor by measuring rates of oxygen consumption. Mothers with their brood in the mouth expended 15.7% more energy than mothers without their brood and 13.8% more than starving nonreproductive controls. After subtracting the energy expenditure of the brood, the excess is reduced to 4.7% and 3.2%, respectively, a difference that is not statistically significant. By contrast, feeding nonreproductive females expended more than twice as much energy as the other groups. We conclude that mouthbrooding is a low-cost strategy profiting from investments made during the preceding nonreproductive phase. The implications for the evolution of mouthbrooding are discussed within the context of ecological constraints.