| Cotesia vestalis is the dominant endoparasitic wasp,parasitizing the immature stage of the diamondback moth(DBM),Plutella xylostella,and has a good control effect on the occurrence of DBM population.In recent years,the frequent occurrence of extreme high temperature has caused immeasurable impacts on the function and biodiversity of agro-forestry ecosystem.How the parasitoid as the third trophic level responds to high temperature stress,which may have an important impact on the biological control effect of controlling insect pests with parasitoid.In this study,the response of the pupae of different ages of C.vestalis to short-term high temperature stress was studied.Firstly,the changes of the duration of different day age pupae of C.vestalis under short-term high temperature stress.Secondly,the physiological changes of pupae of different day age under high temperature stress were studied.Thirdly,the biological changes of the emergence rate,adult sex ratio,body size and adult longevity were studied.Finally,the effects of high temperature stress on the development of adult ovary and oogenesis were studied.The main results are as follows:1.The effects of short-term high temperature stress on the pupal development period,emergence rate and biological characteristics of adults.The emergence rate of the pupae at the same day of age decreased significantly with the increase of temperature.The emergence rate of the one-day-old pupae was 0 after being treated at 40℃;the emergence rate of two-day-old and three-day-old pupae decreased by62.26% and 57.63% respectively compared with the control.After one and two-day-old pupae were treated at 25℃-35℃,the developmental period of pupae shortened with the increase of temperature,the sex ratio increased,and the life span of female and male adults shortened.After the pupae of two-day-old were treated at 40℃ treatments,the pupal duration of pupae was significantly extended,the proportion of females decreased,and the lifespan of female and male adults shortened.After the pupae of three-day-old were treated at 25°C-40°C,the development period of pupae shortened first and then prolonged,the proportion of females increased,the adult lifespan shortened,and the size of adults increased.2.The effects of short-term high temperature stress on the activities of protective enzymes in different day age pupae of C.vestalis.The activities of protective enzymes in pupae of different day age were different after high temperature stress.The POD activity of the pupae of C.vestalis increased with the increase of temperature,and the POD activity of two and three-day-old pupae was significantly higher than that of the control.The CAT activity of pupae increased first and then decreased with temperature increase,and the CAT activity of two-and three-day-old pupae was significantly higher than that of the control,while the CAT activity of one-day-old pupae was not significantly different from that of the control.The SOD activity of one-day and two-day-old pupae first increased and then decreased with the increase of temperature,while SOD activity of three-day-old pupae increased with the increase of temperature.3.The effects of short-term high temperature stress on the ovarian development and oogenesis of C.vestalis adults.The development of the ovarian tube and oogenesis promoted after pupae were treated at 25-35°C,the length of ovarian tube increased and the number of mature eggs increased significantly.The relationship between the stress temperature of pupae and the fastest ovarian development speed is that the best temperature for one-day-old pupae is 30℃,and the best temperature for two-and three-day-old pupae is 35℃.After the pupae were treated at 40℃,there were no significant differences in the length of the ovarian tubes of adults with the control group,but the ovarian development in the treatment group was significantly lagged behind that in the control group,and the boundary between the mature area and the occurrence area in the ovarian tubules and the number of the mature eggs in the ovarian tubes were lower than that in the control.In conclusion,high temperature stress in pupa stage adversely affects physiological and biological parameters such as emergence rate,sex ratio,protective enzyme activity,and different parameters have obvious day-age specificity and sex difference.Short-term temperature stress in pupal stage can promote ovarian development and egg maturation.In order to achieve the best control effect,short-term temperature treatment of pupae of different days of age can be carried out according to the population dynamics before releasing the pupae of C.vestalis. |
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