Preliminary Studies On Parasitic Mechanism Of Pyemotes Zhonghuajia To Semanotus Bifasciatus

Semanotus bifasciatus is a trunk borer, which could bring serious damage to the cypress trees. In recent years, Pyemotes zhonghuajia are found to be the natural enemy to Semanotus bifasciatus by parasitizing in them and killing their larva and the parasitic effects are quite good. However, the research of the parasitic mechanism for Pyemotes zhonghuajia is rarely involved. With the larva of Semanotus bifasciatus taken as to experiment object and based on the developmental zero and effective accumulated temperature of Pyemotes zhonghuajia under the measured constant temperature, the research focuses on Pyemotes zhonghuajia’?, preference for the wound in the larva of Semanotus bifasciatus, as well as the host’s physiology and biochemistry when the pyemotes are parasitizing.1. Under the constant temperatures of16℃,20℃,24℃,28℃,32℃, we look into the influence of different temperatures on the growth of Pyemotes zhonghuajia. We find that the time between feeding and producing offspring of Pyemotes zhonghuajia becomes shorter with the rise of the temperature. The longest one is18.29days when the temperature is16℃, and the shortest4.79days under32℃. The developmental zero and effective accumulative temperate calculated on the basis of developmental durations under different conditions are10.25℃and96.71day degree respectively.2. We use the Six-radiation arms frame to observe the selective differences between the hosts with mechanical wound and the healthy hosts for Pyemotes zhonghuajia. The research shows that after entering the Six-radiation arms frame for8-12hours, Pyemotes zhonghuajia have obvious preference to Semanotus bifasciatus larva with mechanical wound, comparing with the healthy ones. With time process, the attractiveness of the wound to the pyemotes gradually declines after12hours of the entering. And after24-48hours, there is no significant difference between them for the pyemotes. This indicates that Pyemotes zhonghuajia have a strong tendency to the wound of the hosts. But the tendency declines with time process. And the selective differences between the hosts with mechanical wound and the healthy hosts for Pyemotes zhonghuajia disappear.3. We use the method of SDS-PAGE to analyze the content of the hemolymph protein and the type changes of the infected Semanotus bifasciatus larva. The results show that the molecular weight distribution of the hemolymph protein of Semanotus bifasciatus larva spreads between97.4and14.4kDa. The band abundance of some hemolymph proteins has some changes in different periods of the parasitism, which means the content change of the content of proteins. We also discover some newly added protein bands in the midterm of the parasitism. We guess the immunoreaction of the host insect parasited by Pyemotes zhonghuajia takes place.4. We use the amino acid analyzer to measure and analyze the content of the heinolymph free amino acid of Semanotus bifasciatus larva which is parasitized by Pyemotes zhonghuajia. There are15kinds of free amino acids detected from the hemolymph of Semanotus bifasciatus larva. In the whole observation phase, the gross content of the hemolymph free amino acid of Semanotus bifasciatus larva shows a variation tendency of decreasing in the initial stage, increasing in the interim and decreasing again in the later stage. The proline and valine of the major amino acids and the glycine of the rare amino acids have the same variation tendency as the gross content of the amino acids. All of the other12types of amino acids have a content change in different periods of the parasitism.