Oxytetracycline (OTC) is commonly used for aquaculture and livestock, and its environmental concentration has increased to a considerable level and displays potential environmental risk. In the present study, the life-table demography of Brachionus calyciflorus exposed to sublethal concentrations (30.0, 60.0, 90.0, 120.0, 150.0 and 180.0 mg L−1) of OTC was investigated at 1.0 × 106, 2.0 × 106 and 4.0 × 106 cells mL−1 of Scenedesmus obliquus. The results showed that at each algal density, OTC concentration affected significantly life expectancy at hatching, net reproductive rate, generation time and intrinsic rate of population increase (P < 0.01), but did not affect proportion of mictic offspring of the rotifers (P > 0.05). Compared to the controls, and at 2.0 × 106 cells mL−1 of S. obliquus, treatments with OTC at 30.0–150.0 and 60.0–120.0 mg L−1 significantly prolonged life expectancy at hatching and generation time, treatments with OTC at 30.0–120.0 and 30.0–90.0 mg L−1 increased net reproduction rate and intrinsic rate of population increase, respectively, but the reverse was also true for those with OTC at 180.0 mg L−1. Higher and lower algal densities decreased the magnitude of stimulatory effects of lower concentrations of OTC but enhanced that of inhibitory effects of high concentration of OTC on the survival, asexual reproduction and population growth of the rotifers. At the three algal densities, net reproduction rate was more sensitive to OTC than the other endpoints, and significant concentration- effect relationship existed between OTC concentration and each of all the life-table demographic parameters except the proportion of mictic offspring.
Differences in life table demography among eight geographic populations of Brachionus calyciflorus (Rotifera) from China
