Costs of delayed mating opportunities, overripening, and mate choice in Killifish

Females of highly iteroparous, oviparous species must mate multiply and potentially choose mates hundreds to thousands of times throughout their lifespan. Theory indicates that costly female mating preferences may favor low levels of preference in species that have to mate repeatedly. One potential cost of mating preference is overripening, which occurs in some external fertilizers when females ovulate but do not spawn their eggs. Overripening may create a trade-off between the benefits of mate choice (i.e., rejecting males of poor quality) and egg viability. This study tested for overripening as a cost of delayed mating and determined its effects on female mating preferences in the bluefin killifish, Lucania goodei. Female L. goodei often mate multiple times each day across multiple days when gravid. Females were divided into three treatments: mate every day, mate every two days, and mate every four days. In the first experiment, females were paired with either a red or a yellow conspecific male on spawning days.  In the second experiment, females were paired with either a conspecific male (L. goodei) or a heterospecific male (L. parva) on spawning days. In both experiments, the eggs were retrieved following spawning, and their viability (i.e., survival) was monitored for five days. Females that were forced to ‘hold onto’ their eggs for extended periods had smaller clutch sizes and lower egg viability, demonstrating that costs to rejecting males potentially exist. In the first experiment, there was no evidence of female choice for red versus yellow males. In the second experiment, female preference for conspecifics versus heterospecifics declined when females could only mate once every four days, but the differences among treatments did not reach statistical significance. The results of this study illustrate a potential cost to female mate choice and suggest that the benefits of mate choice may not outweigh the costs due to egg overripening.

Methods
We collected bluefin and rainwater killifish. We conducted two experiments. In the first, females were allowed to mate daily, every other day, or once every four days. The goal was to determine whether egg viability decreased when females were precluded from spawning daily. We also sought to determine whether decreases in egg viability due to overripening caused a decrease in female mating preference. In the first experiment, female L. goodei could spawn with either a red or yellow color morph of their own species. Females were paired either every day, every other day, or once every four days with either a red or yellow male and given the opportunity to spawn for four hours. After this time, the eggs were collected, counted, and their survival to hatching was recorded. In the second experiment, female L. goodei were allowed to spawn with either a conspecific L. goodei male or a heterospecific L. parva male. Again, on spawning days, females could spawn for four hours. The eggs were then collected, counted, and monitored for survival until hatching. 

We used these data to examine the effects of holding females on egg survival. We also compared the number of eggs laid with either red or yellow males (experiment 1) or conspecific or heterospecific males (experiment 2). 

The data sets have information on the replicate female, the treatment, the identity of the male, the number of eggs obtained, and the number of eggs that eventually hatch.