CONICET | Buscador de Institutos y Recursos Humanos

The decline in fitness components with age is variable among different taxa, and includes changes in fertility and brood quality. In the present study we selected Neocaridina davidi, a freshwater shrimp with direct development, to analyze juvenile quality and female reproductive performance over successive spawnings, which correlate with female age. Given the high costs of reproduction in species with direct development, we hypothesized that female reproductive performance and juvenile quality decrease in advanced spawns.Two experiments were performed. In Experiment 1, we evaluated the reproductive performance of N. davidi females and juvenile quality (through a food restriction test) over the first six successive spawnings. In Experiment 2, we analyzed the lipid and protein contents in juveniles from the third, fourth and fifth spawns, after feeding them daily or starving them for the initial 8 and 12 post-hatching days. Female mortality was observed throughout Experiment 1, along with a decrease in the proportion of ovigerous females over successive spawns. However, the interspawning interval and the number and size of newly hatched juveniles were similar among spawns. Moreover, females that spawned many times had a similar reproductive efficiency to those that spawned few times, as evidenced by a similar percentage of broods successfully hatched and percentage of broods with more than 28 juveniles among spawn numbers. Overall, these results may indicate a partial effect of multiple spawning on female reproductive performance. Growth, survival and biochemical composition of food-restricted juveniles showed similar or even higher values in advanced spawns as compared to the first spawns. This is, to our knowledge, the first empirical demonstration in a decapod crustacean with direct development that, although the percentage of ovigerous females decreases over time, other reproductive variables and juvenile performance do not decline in successive spawnings, at least for the initial six consecutive spawns.