| Dastarcus helophoroides(Coleoptera: Bothrideridae)is a natural enemy insect,and has been widely used for biological control of long-horned beetles.At present,the forest mainly uses artificial release of large amounts of adult insects for the control of longicorn beetles,but in practice,little attention is paid to the release of adult insect age,and there are also some phenomena where the control effect is not obvious.In order to explore the impact of adult insect age on control effectiveness,we used adults of D.helophoroides at different months of age artificially bred in the laboratory as experimental materials.By measuring the body weight,length,and antioxidant enzyme activity of adults,dissecting and observing the abdominal cavity and reproductive system of females,as well as analyzing the growth and development status of offspring,which is ordered to obtain the relationship between the adult age of the parasitic natural enemy insect and its vital signs,reproductive ability,and offspring development status.To provide theoretical guidance for the artificial breeding and forest release of D.helophoroides.The main results are as follows:(1)By measuring the body weight and body length of male and female adults of D.helophoroides at 2,4,6,8 and 12 months of age,it was found that there was a linear relationship between the weight and body length of both female and male adults at the same months of age.The weight of both female and male adults of the same body length of D.helophoroides decreases with increasing months of age.From the dissection of male and female adults of D.helophoroides at different months of age,it was found that the abdominal cavity of adults exhibits varying degrees of shrinkage phenomenon.As the age of the adult increases,the proportion of abdominal cavity shrinkage in female and male adults increases.Among them,the proportion of the abdominal cavity of female and male adults with shrinkage phenomenon at 4 months of age was 79.17% and 75.83%,respectively.The average shrinkage degree of abdominal cavity in female and male adults showing shrinkage phenomenon also increases with monthly age.Among them,the average degree of shrinkage in the abdominal cavity of female and male adults showing shrinkage phenomenon at 4 months of age was 27.17%and 25.81%,respectively.(2)The superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities were measured by hydroxylamine,guaiacol and ammonium molybdate assays of male and female adults of D.helophoroides at 2,4,6,8 and 12 months of age.The results showed that the antioxidant enzyme activity in female insects showed different patterns of change with the increase of monthly age,with SOD activity showing an upward trend,POD activity showing a first upward and then downward trend(The enzyme activity was highest at 4 months of age),and CAT activity also showed a first upward and then downward trend(The enzyme activity was highest at 6 months of age,reaching 23.54 U/mg protein).However,the SOD,POD,and CAT activities of male insects at different months of age were relatively stable,and there was no significant difference between insect ages.(3)The female reproductive system of D.helophoroides at 2,4,6,8 and 12 months of age was observed using microanatomy techniques.It was found that as the monthly age increased,the morphology of the ovaries gradually shrunk,the morphology of gradually developing oocytes in the ovarioles became small,and the number of mature eggs in the ovaries decreased.The average number of mature eggs at 2 months of age was 109.3,4 months of age was 41.7,and 12 months of age was 3.9 only.Using RT-q PCR technology,the relative expression of two genes that play an important regulatory role in ovarian development was analyzed.The results showed that the relative expression of vitellogenin gene(Vg)increased with monthly age of the female adults,showing a trend of first decreasing,then recovering,and then decreasing,with the highest expression level at 2 months of age;The relative expression of vitellin receptor gene(Vg R)decreased with monthly age,with the lowest expression level occurring at 12 months of age.(4)Statistics on egg production and offspring growth and development parameters of adults of D.helophoroides at 2,4,8,and 12 months of age showed that the monthly egg production of a single female decreased gradually with increasing age,with the largest monthly egg production of 340.65 at 2 months of age,73.46 at 4 months of age and only 9.02 at 12 months of age.The hatching period of eggs laid by adults at 2 months of age was 9.40 d,which was significantly shorter than that of eggs laid by 4 months of age adults(10.35 d).The hatching rate of eggs laid by adults of D.helophoroides at 2,4,8 and 12 months of age was higher than 90%.The parasitism rate of offspring larvae at 2 and 4 months of age was significantly higher than that at 8 and 12 months of age.The developmental duration of offspring at 2 and 4 months of age was significantly shorter than that at 8 and 12 months of age.The preoviposition duration of the offspring of adults of 2 months of age was significantly shorter than that at 4,8 and 12 months of age.The results showed that with the increase of monthly age,the amounts of eggs laid by adults decreases,the parasitism rate of offspring larvae decreases,and the growth and development time of their offspring lengthens.In summary,the vital signs,ovarian development and offspring growth and development status of adults of D.helophoroides decreased with increasing monthly age,and only the adults below 4 months of age showed better performance in all indexes,and 2 months of age was the best.This study can provide theoretical guidance for the design of artificial breeding program and the age matching of insects released in the forest. |
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