| Ovomermis sinensis is a widespread species in China. It is an insects’ natural enemy which have a great potential for biological control. But it has not been successfully cultured in vitro yet, so inhibit the development and application of this biological insecticide. The causes mainly attributed to little is known about the Entomopathogenic nematodes and mechanism of sex determination. Thus, mechanism research of sex determination is importance of theoretical significance and practical value.In the present study microwave digestion and ICP-AES were used to determinate the dynamic changes of seven kinds of trace elements in the male and female nematodes and hemolymph of their host insect during the critical period of sex determination. These seven kinds of trace elements are Fe, Zn, Cu, Ca, Mg, Mn and Se. And reagent kit was used to determine the activities of six kinds of digestive enzymes of O. sinensis and its host hemolymph during the critical period of sex determination. These digestive enzymes are AMS, Pepsin, LPS, SOD, CAT and POD. Following that, we determined the titer of JH3and20E of hemolymph of the host by using the high performance liquid chromatography (HPLC) during the critical period of sex determination of nematode. Finally, data statistics and analysis was conducted. And the results are showed as follows.Firstly, trace elements:(1) All trace elements nematode needed in the process of growth and development come from the hemolymph of host. About two days was needed when these trace elements were absorbed through the body wall of nematode and converted it into their own nutrition.(2) The sex determination of nematode completed when the parasitic period of growth and development ends. The critical period of sex determination of male nematode starts when it has inhabited in host for about3days, while the critical period of female is about5days. Therefore, male is earlier than female for about2days. After parasitizing in host for7days, the sex determination of nematode tends to complete. The sex determination of male or female has been completed after prolapse2days.(3) Many factors influenced the sex determination of nematodes, such as copper, selenium and manganese and so on. And copper is closed related within the sex determination of female, and the selenium and manganese for male.Secondly, enzymes:(1) There are Pepsin and AMS in the nematodes. During the parasitic stages, the AMS activity increased gradually and reached the maximum after3days, and then decreased gradually. While the Pepsin activity began to increase rapidly from the fifth day to the seventh day, and there were no significant difference before these days; Higher CAT, SOD activity achieved on the3rd day of parasitic period, and fall after5day, and rise again after7day. The POD activity has maintained constantly since the nematode parasitic in the host for three days.(2) Digestive enzymes activity changed simultaneous between nematode and the host; and the change of protective enzyme activity has a linear relationship between nematode and the host, but the nematode lags behind their host2days.(3) During the parasitic stages, female nematode has higher digestion and metabolism level than male. The first differences between male and female nematodes appeared when parasitic for3and5days. The present work provides a theoretical basis for the metabolism of nutrient digestion and absorption and the mechanism of sex determination of O. sinensis.Finally, hormone:(1) Compared with control group, experimental group have following results. The titer of JH3exists significant difference when the nematodes parasitic host3th,5th, and7th day (P<0.01); and the titer of20E has the same result in3rd day. The titer of JH3and20E increased sharply after the third day and decreased significantly at the fifth day. Whereas, no significant differences was found at the fifth day for20E. The titer of JH3increased significantly again after the7th day. The titer of20-E of male’s host is higher than female’s host and control group, and the latter two are equal. Second, when comparison host of female and male nematodes, the first difference of the titer of JH3was found at the third day of parasitic stage.(2) In addition, the juvenile hormone of host makes more obvious effect on female host than male host. While the first difference of the titer of molting hormone appeared at the seventh day. When comparison the effect made by titer of molting hormone, we found that female’s host was less obviously effected than male’s host.From the two perspectives of the nutrition requirement of nematode and supply by host, we firstly determined and analyzed the trace elements, enzymes, hormones during the critical period of sex determination of the O. sinensis. This study provides a theoretical basis for the discipline of nutrition metabolism and the mechanism of sex determination of O. sinensis. Meanwhile, it laid the foundations for culture O. sinensis in vitro. |
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