Effect of deltamethrin on experimental population dynamics of freshwater rotifer Brachionus calyciflorus

摘要

Using life-table techniques, we studied the effect of deltamethrin whose experimental concentrations were 0.6, 1.2, 1.8, 2.4, 3.0 and 3.6 mg/L on experimental population dynamics of freshwater rotifer Brachionus calyciflorus at 25 ℃ and with 3.0 × 10⁶ cells/ml of alga Scenedesmus obliquus as the rotifer’s food . The results showed that deltamethrin shortened the survival time , and lowered the fecundity of the rotifer. When the concentration of deltamethrin was 3.6 mg/L, the survival time and fecundity of the rotifer was the shortest and lowest, and was 72 h and less than 1offspring/female/8h, respectively . Compared to the control, deltamethrin ranged from 0.6 to 3.0 mg/L prolonged the pre-reproductive period significantly from ( 16.48 ± 0.30 ) h to ( 20.95 ± 0.97 ) h , except 1.2 mg/L of deltamethrin at which the pre-reproductive period was ( 15.83 ± 0.29 ) h . The reproductive periods of the rotifer treated with 0.6 and 1.2mg/L of deltamethrin were respectively ( 89.83 ± 2.30 ) h and ( 106.58 ± 4.88 ) h, and were significantly longer than that of the control which was ( 78.29 ± 2.89 ) h; while those treated with 2.4 and 3.0 mg/L of deltamethrin were respectively ( 70.13 ± 2.61 ) h and ( 48.14 ± 2.52 ) h, and were significantly shorter than that of the control. 1.2mg/L of deltamethrin lengthened the mean life span significantly. The life expectancy, generation time, net reproductive rate and intrinsic rate of population increase of the rotifers decreased respectively from ( 135.62±6.37 ) h, ( 58.81±1.62 ) h, ( 28.47±0.59 ) ind. and ( 0.0802± 0.0026 ) /h to ( 81.39±5.04 ) h, ( 46.31±2.12 ) h, ( 6.32±2.11 ) ind. and ( 0.0431±0.0126 ) /h with the rise of deltamethrin concentration from zero to 3.0 mg/L. The net reproductive rate was more sensitive than the intrinsic rate of population increase, because the lowest concentration that the net reproductive rate began to differ significantly from the control was 1.2 mg/L, but for the intrinsic rate of population increase it was 2.4 mg/L [ A cta Zoologica Sinica 51(2): 251 - 256 , 2005] .