One purpose of this research is to present accumulation of cadmium （Cd） and copper （Cu） by female Oxya chinensis （Orthopera： Acridoidea） in a simulated soil-plant-insect ecosystem treated with Cd. Fourth-instar nymphs of O. chinensis had been fed on wheat （Triticurn aestivum） seedlings contaminated with Cd and Cu for one month. In the ecosystem, the Cd concentration in wheat seedlings rose greatly with the increasing of Cd in the soil, but the Cu concentration in wheat seedlings was not found elevated. There was a highly significant difference（P〈0.05） in Cd concentrations of wheat seedlings and not any significant difference（P〉0.05） in Cu concentrations of wheat seedlings. The Cd and Cu concentration in different body part-head, thorax, abdomen, and hind femur, varied under different Cd concentrations in soil. There were significant differences （P〈0.05） in the four parts of Cd and Cu accumulations with all treatments. The order of Cd accumulation was thorax 〉abdomen 〉head 〉hind femur and the Cu was abdomen 〉thorax 〉 head〉hind femur. The results indicated that Cd and Cu were accumulated from the soil to grasshoppers through the plant; that is to say, Cd and Cu in environment could be transported to animal or human via food chain.
LI Li-junLIU Xue-meiDUAN Yi-haoGUO Ya-pingCHENG BinGUO JunXI Yu-yingMA En-bo
Specific activity, substrate specificity, and kinetic parameters （Km and Vmax） of glutathione S-transferases （GSTs） towards three substrates, 1-chloro-2,4-dinitrobenzene （CDNB）, 1,2-dichloro-4-nitrobenzene （DCNB）, and p-nitrobenzene chloride （pNBC） were investigated in six tissues （foregut, midgut, hindgut, fat body, hemolymph, and muscle） of Oxya chinensis. In addition, the inhibition in vitro （ethacrynic acid, and Cibacron Blue 3GA） of Oxya chinensis in the six tissues was also investigated. Glutathione S-transferase activity was detected in all the six tissues examined. The rank order of GST activities towards CDNB was fat body 〉 midgut 〉 hindgut 〉 muscle 〉 foregut 〉 hemolymph both in females and males. Glutathione S-transferase activities in the fat body in females and males were 1.3- to 10.4-fold and 1.1- to 10.0- fold higher than those in the other tissues. The rank order of GST activities towards the other substrates changed slightly. From these results, it was inferred that GSTs in the fat body and midgut played important roles in detoxifying xenobiotics including insecticides and plant allelochemicals in O. chinensis. In the three substrates examined, CDNB seemed to be the best substrate, followed by pNBC and DCNB. The kinetic parameters of GSTs were different among the six tissues. This suggested that GSTs in different tissues have various affinities and catalytic efficiency to substrates. In vitro inhibition study showed that the median inhibition concentration （IC50） values of the two inhibitors to GSTs from the six tissues were different. The results suggested that the two inhibitors have different inhibition potency to GSTs from the different tissues. The observed changes in kinetic parameters and inhibition in vitro among the six tissues of the insect might suggest that the number and structure of isoenzymes and their rate of expression varied for the different tissues.
Carboxylesterases （CarEs） from two field populations of the oriental migratory locust, Locusta migratoria manilensis （Meyen）, were examined to try to understand their contribution to malathion insensitivity. The CarEs activities in Wudi population （WD） were 1.75- and 1.50-fold significantly higher than those in Huangliu population （HL） when a-naphthyl acetate （a-NA） and [3-naphthyl acetate were used as substrates, respectively. Such elevated CarEs activities presented in the WD could be because of an increased staining intensity of the a-NA-hydrolyzing CarEs as shown on the nondenaturing polyacrylamide gel electrophoresis. Inhibition studies of CarEs using paraoxon and malaoxon indicated that CarE activities in the HL were more strongly inhibited than those in the WD. Furthermore, a 449-bp DNA fragment of CarE was obtained from L. migratoria manilensis. Hemiquantity reverse transcription-polymerase chain reaction analysis showed that CarE gene expression level in the WD was higher than that in the HL. The higher CarE activities and the increased CarE mRNA level in the WD appeared to be associated with decreased susceptibility to malathion in the WD due to the application of organophosphorus insecticides.
YANG Mei-ling ZHANG Jian-zhen ZHANG Jian-qin GUO Ya-ping MA En-bo
Genetic relationship among Oxya chinensis populations and Oxya japonica populations collected from Xuzhou City, Jiangsu Province and Pingshan County, Hebei Province, China were analyzed by random amplified polymorphic DNA （RAPD） markers. A total of 125 DNA bands ranging from 200 to 2 200 bp were amplified by 10 random primers in DNA samples from 43 grasshopper individuals. One hundred and twenty-three （99%） of these bands were polymorphic. Shannon＇s index showed that the genetic, diversity within O. chinensis （0.3432） was higher than that of O. japonica （0.2781）. Nei＇s genetic distance between O. chinensis population and O. japonica population from the same area was less than that between populations from two different areas. The dendrogram based on Nei＇s genetic distance of RAPD markers was constructed using the unweighted pair group method with the arithmetic average （UPGMA） and Neighbor-Joining （NJ） methods. Cluster analysis indicated that all the individuals were grouped into two main clusters. O. chinensis populations from Xuzhou and Pingshan formed one cluster, and O. japonica populations from the two regions belonged to another cluster. The results demonstrated that RAPD can detect within species, and among closely related species. polymorphisms to distinguish minor difference among individuals
