The Distribution And Bioaccumulation Effects Of Trace Elements Concentrations In Nilaparvata Lugens (Stal) And Sogatella Furcifera (Horvath)

This study is subsidized by the China National High-Tech Program (863 Program) (2006AA10Z217). This work provides a modified exponential equation evaluating the change of the weight of Nilaparvata lugens (Stal) and Sogatella furcifera (Horv a th), and the equation divides the body weight into two components, organism weight and contents weight. Then the temporal changes of elemental concentrations in treated Nilaparvata lugens and Sogatella furcifera were detected using inductively coupled-plasma mass spectrometry. Based on changes in weight and in organism metal concentrations, the distribution and bioaccumulation effects of elemental concentrations in Nilaparvata lugens and Sogatella furcifera were analyzed by the model.Either Nilaparvata lugens or Sogatella furcifera is the long distance migratory insect feeding on rice plant and threathening the growth of rice. So the ultimate aims of this study were to establish a new method to study the pattern of metal elements accumulation, through the combination of biological modeling and experimental data; and to study the distribution and bioaccumulation effects of different elements in Nilaparvata lugens and Sogatella furcifera, through the analysis of the chemical elements. The study maybe is a potential chemical fingerprinting method for monitoring the source area of Nilaparvata lugens and Sogatella furcifera migration. Followings are the main results of this study:1. To detect the temporal changes of metal elemental concentrations by ICP-MS, the test insects, adults of the Nilaparvata lugens and Sogatella furcifera were artificially reared with de-ionized water on 24 h,48 h, and 96 h, respectively. Then a modified exponential equation was developed to model the weight changes over time. The entire weight of Nilaparvata lugens and Sogatella furcifera was assumed to be divided into two components, its organism weight (O) and its contents weight (E) in the alimentary canal. The decreased rate of excretion is r. Therefore, weight of the test insects at different times can be expressed by this model, Wt= O+E(1-r)t. Different developmental periods of the adult of Sogatella furcifera were artificially reared with de-ionized water to verify the model validity. The results show that this model can effectively estimate the organism weight and the contents weight, and the respective proportion of the total weight.2. With this modeling, the metal elements were divided into three groups based on their temporal change in concentration in Nilaparvata lugens. Trace element concentrations in the three groups respectively displayed bio-accumulation, dynamic balance, and bio-elimination. In the first group, the concentrations of Na, Zn, and Cd were significantly higher in the organism than in excreta and thus represented bio-accumulation. The probable reason for this phenomenon is that the uptake rates of these elements exceeded excretion rates when the organism was in a stable condition. In the second group, the concentrations of nine elements (K, Mg, Ca, Fe, Cu, Ba, Sr, Ni, and Sn) showed no significant difference in concentrations between the organism and excreta. They exist in the body maybe with the way of a dynamic equilibrium. In the third group, the concentrations of Al, Mn, Rb, Pb, and V were significantly lower in the organism than in the excreta. These elements, which probably are found in the alimentary tract and excretory system more than in other organs, were excreted by the excretory system and only a small portion was stored in the body. Model results well reflected the disposition of the trace elements detected in the Nilaparvata lugens.3. The concentrations of these elements in Sogatella furcifera were estimated by modeling. The results showed that the concentrations of Cu, Zn, Cd, Mn and Ca are significantly higher in the organism than in the excretion, and show significant bioaccumulation in Sogatella furcifera; seven of the elements (Fe, Na, As, U, Mg, K and Pb) have no significant difference between the organism and excretion. Probably the concentrations of these elements in the organism are balanced with the concentrations in the excretion so that the body concentration no significant changed.In this study, the modified exponential model was established to describe the dynamic process of contents change in the Nilaparvata lugens and Sogatella furcifera. And the study reveals the different elements in Nilaparvata lugens and Sogatella furcifera with different characteristics of distribution and bioaccumulation effects (Such as Zn and Cd). The kinetic model should provide significance reference for studies involving metal or metalloid accumulation in other insects.