Effects of maternal phosphorus deficiency on reproductive allocation of the copepod Pseudodiaptomus annandalei Sewell, 1919

摘要

The nutrient status of phytoplankton affects the reproductive traits of zooplankton, yet no study has addressed how reproductive allocation varies with phosphorus (P) availability in copepods. We hypothesized that maternal P deficiency reduces reproductive investment in copepods and that interactions exist between maternal and postnatal P condition effects on offspring development. Females of the copepod Pseudodiaptomus annandalei were fed algal prey with different P contents, then allocation of elements and fatty acids in offspring and naupliar development of offspring were measured. Females reduced total reproductive efforts and P investment per offspring under P-deficient conditions. Gross reproduction efficiency of P and the proportion of available maternal P invested in reproduction increased as P consumption decreased, revealing priority of reproductive investment under P deficiency. A high proportion of body docosahexaenoic acid was allocated into reproduction, regardless of the dietary P condition. Duration of naupliar phase and body length at stage CI in offspring were independent of the initial maternal P investment, implying a low P demand for early copepod development. As such, female copepods may down-regulate P investment per offspring to offset impairment of P deficiency on their fitness, and to maximize number of offspring at a given level of P availability.