Strategic egg allocation in the zebra fish, Danio rerio

Females across a range of taxa have been shown to differentially allocate their reproductive resources according to the attractiveness of their mate. Previous studies demonstrated a female preference for larger males in the zebra fish but have so far failed to uncover a size-mediated difference in male mating success, possibly due to the effects of male--male competition. By controlling for male--male competition in the present study, we show that females strategically allocate their reproductive resources (i.e., eggs) toward larger males. When females were mated sequentially with a large and small male, they released a greater number of eggs to the second male when he was large than when he was small. Furthermore, there was also a trend for females to release a greater proportion of their eggs to the first male when he was large. Across females, the total number of eggs laid by each female increased with the average standard length of the male pair, whereas the number of eggs laid to the second male also increased with his standard length. This study represents one of the first attempts at identifying differential allocation in a resource-free egg scatterer and suggests that female preferences may play a greater role in the reproductive success of males in this species than previously envisaged. Copyright 2007, Oxford University Press.